Book II. Deviations from the Ordinary Form of Organs

In a morphological point of view the form of the various parts or organs of plants and the changes to which they are subjected during their development are only second in importance to the diversities of arrangement and, indeed, in some cases, do not in any degree hold a second place.

Taken together, the arrangement, form, and number of the several parts of the flower, make up what has been termed the symmetry of the flower. Referring to the assumed standard of comparison, see p. 4, it will be seen that in the typically regular flower all the various organs are supposed to be regular in their dimensions and form. At one time it was even supposed that all flowers, no matter how irregular they subsequently became, began by being strictly symmetrical or regular, and that subsequent alterations were produced by inequality of growth or development. The researches of organogenists have, however, dispelled this idea of unvarying primordial regularity, by showing that in many cases flowers are irregular from the very first, that some begin by being irregular, and subsequently become regular, and even in some cases resume their original condition during the course of their development. Under these circumstances an artificial standard of comparison becomes almost an absolute necessity for the time being.

Changes of form very generally, but not always, are accompanied with a change in regularity: thus a flower habitually bi-lateral may assume the characters of radiating symmetry and vice versâ. Increase or decrease of size very frequently also are co-existent with an alteration in the usual form.

In the case of the arrangement of organs it is often difficult or impossible, in the present state of our knowledge, to determine whether a given arrangement is congenital or acquired subsequently to the first development, whether for instance an isolation of parts be due to primordial separation or to a subsequent disunion of originally combined organs, see p. 58. With reference to the changes in the form of organs, however, it is in general more easy to ascertain the proximate cause of the appearance, and thus teratological changes of form may be grouped according as they are due to, 1, arrest of development; 2, undue or excessive development; 3, perverted development; and 4, irregular development; hence the use of the following terms—Stasimorphy, Pleiomorphy, Metamorphy, and Heteromorphy—to include teratological changes really or apparently due to one or other of the causes above mentioned. The classification here adopted is of course to a considerable extent an arbitrary one and subject to correction or modification, as the knowledge of the development of the flowers in the various genera of plants advances.

Part I. Stasimorphy.

Deviations from the ordinary form of organs arising from stasis or arrest of development are included under this heading.

There are many cases in which the forms proper to a juvenile condition of the plant are retained for a much longer period than ordinary, or even throughout the life of the individual growth goes on, but "development" is checked. Such conditions may even be propagated by seed or bud. It is a very general thing for botanists to consider these cases as reversions to a simpler, primitive type, and this may be so; but on the other hand, they may be degenerations from a complex type, or they may have no direct relation to any antecedent condition. Stasimorphic changes affecting principally the relative size of organs—such, for instance, as the non-development of internodes, or the atrophy or suppression of parts will be found mentioned in the sections relating to those subjects. In the present part those alterations which affect the form of organs principally are treated of.

Chapter I. Persistence of Juvenile Forms.

The retention in adult life of a form characteristic of an early stage of development, and therefore usually transient, may be manifested in any of the organs of the plant. As these cases are for the most part treated under separate headings, it is here only necessary to allude to a few, which it is difficult to allocate satisfactorily, while the reader may be referred for other instances of like nature to the sections on Peloria, Atrophy, Suppression, Dimorphy, Substitutions, &c.

Stasimorphy in the leaves of conifers.—In many conifers the leaves produced in the young state of the plant are different, both in arrangement and form, from those subsequently developed (see pp. 89, 90). But it occasionally happens that the plant continues to form throughout its existence leaves such as are usually produced only in a young state; thus M. Gubler ('Bull. Soc. Bot., Fr.,' vol. viii, 1861, p. 527) describes a plant of Pinus pinea in which the primordial, usually transitory, foliage was permanent, leaves of the ordinary shape not being developed at all. It more often happens that some only of the leaves retain their young form while others assume other shapes, see fig. 115. This happens frequently in the larch and constantly in the Chinese juniper when it has arrived at a considerable age. In Cupressus funebris two forms of leaves may often be found on the same plant, the one representing the juvenile state, the other the more developed condition. What is very singular, is that a cutting taken from the branch with leaves of the young form grows up into a shrub bearing leaves of no other shape, so that an ordinary observer unacquainted with the history of the plant would imagine that he had to deal with two distinct species. This fact is the more interesting when compared with the alternation of generations which takes place among the lower animals.

The regular development of all the parts of the flower in a plant habitually producing irregular flowers is referred to under the head of Peloria, but it still remains to consider those examples in which some only of the parts of the flower are affected in this manner. Most of these cases are elsewhere referred to in this volume under the particular form of malformation assumed; but the following case may here be noticed as not coming under any of the previous heads. It is an instance recorded by Professor Babington ('Phytologist,' August, 1853), and in which the pod of Medicago maculata, which is usually rolled up like a snail shell and provided with spines, was sickle-shaped and unarmed.

Chapter II. Regular Peloria.

When an habitually irregular flower becomes regular, it does so in one of two ways; either by the non-development of the irregular portions, or by the formation of irregular parts in increased number, so that the symmetry of the flower is rendered perfect, as in the original peloria of Linnæus, and which may be called irregular peloria, while the former case may be called regular peloria. This latter appearance is therefore congenital, and due to an arrest of development. As the true nature of these cases has not been in all cases recognised (even Moquin places them under the head of deformities—they being less entitled to rank in that class than are the usual flowers), it may be well to cite a few instances taken from various families. In Delphinium peregrinum I have met with perfectly regular flowers having five sepals and five oblong stalked petals, and a similar occurrence has been noted in other species of this genus. Baillon, in referring to these flowers, points out the resemblance that they bear to the double varieties of Nigella. In the stellate columbines (Aquilegia) of gardens the tubular petals are replaced by flat ones often in increased numbers. In violets both forms of peloria occur, that in which there is an unusual number of spurs, and that in which there are no spurs (var. anectaria). In the more perfect forms of regular peloria occurring in the last-named genus the following changes may be noticed: 1, an alteration in the direction of the flower so that it remains in an erect position, and is not bent downwards as usual; 2, equality of proportion in the sepals and petals; 3, absence of spurs, as also of hairs on the lateral petals; 4, equal stamens whose anthers are sometimes entirely destitute of the prolonged crest which forms so prominent a feature under ordinary circumstances; 5, erect, not curved styles, and the stigmas not prolonged into a beak, but having a more or less capitate form; ovary with three or five cells, ovules normal.

These are cases where the change in question is most strongly marked, the bi-lateral is completely replaced by the radiating symmetry. The absence of the usual nectary, and of hairs on the side petals, the alterations in the form of the style, etc., all show how much the process of fertilisation must be altered from that which occurs under ordinary circumstances. In some of the double violets now cultivated in gardens, a similar regularity of proportion in the parts of the flower may be seen combined with the substitution of petals for stamens and pistils, and with the development of an increased number of petal-like organs. Between these cases and the ordinary spurred forms as well as those with an increased number of spurs, many intermediate forms may be met with. That such regularity should occur in this family is not to be wondered at seeing that there is a whole subdivision of the order (Alsodeiæ) in which regular flowers are the rule.

In cultivated Pelargoniums the central flower of the umbel or "truss" frequently retains its regularity of proportion, so as closely to approximate to the normal condition in the allied genus Geranium; this resemblance is rendered greater by the fact that, under such circumstances, the patches of darker colour characteristic of the ordinary flower are completely wanting; the flower is as uniform in colour as in shape. Even the nectary which is adherent to the upper surface of the pedicel in the normal flower disappears—sometimes completely, at other tunes partially. The direction of the stamens and style, and even that of the whole flower, becomes altered from the inclined to the vertical position. In addition to these changes, which are those most commonly met with, the number of the parts of the flower is sometimes augmented, and a tendency to pass from the verticillate to the spiral arrangement manifested. Schlechtendal mentions some flowers of Tropæolum majus in which the flowers were perfectly regular and devoid of spurs, while in the double varieties, now commonly grown in greenhouses, the condition of parts is precisely the same as in the double violet before alluded to. Among the Papilionaceæ the Laburnum and others have been noticed to produce occasionally a perfectly regular flower in the centre, or at the extremity of the inflorescence, though the peloria in this flower is usually irregular. In the Gentianaceous genus Halenia, H. heterantha is remarkable for the absence of spurs. Amongst Gesneraceæ, Bignoniaceæ, Scrophulariaceæ, and other families of like structure, regular peloria is not uncommon. Fig. 120 represents a case of this kind in Eccremocarpus scaber, conjoined, as is frequently the case, with dialysis or separation of the petals. Many of the cultivated Gloxinias also show erect, regular, five stamened flowers, but these are probably cases of irregular peloria.

A solitary flower of Pedicularis sylvatica was found by the Marquis of Stafford near Dunrobin Castle in Sutherlandshire, in which the usual ringent form of the corolla was replaced by the form called salver-shaped. There were six stamens, four long and two short. Sir W. Hooker and Mr. Borrer are stated to have found a similar flower in the same locality in 1809.

The passage of ligulate to tubular corollas among Compositæ is not of such common occurrence as is the converse change. I owe to Mr. Berkeley the communication of a capitulum of a species of Bidens, in which there was a transition from the form of ligulate corollas to those that were deeply divided into three, four, or five oblong lobes. These then were instances of regular peloria.

In Orchidaceæ a similar change is not by any means infrequent; in a few, indeed, a regular flower is the normal character, as in Dendrobium normale, Oncidium heteranthum, Thelymitra, etc. Fig. 121, reduced from a cut in the 'Gardeners' Chronicle,' 1854, p. 804, represents an instance of this kind in Cattleya marginata.

From the same journal the following account of a case of peloria in Phalænopsis Schilleriana is also cited as a good illustration of this peculiar change. The terminal flower differed entirely from all the others; instead of the peculiar labellum there were three petals all exactly alike, and three sepals also exactly alike; the petals resembled those of the other flowers of the spike, and the upper sepal also; but the two lower sepals had no spots, and were not reflexed as in the ordinary way: thus, these six parts of the flower were all in one plane, and being close together at their edges, made almost a full round flower; the column and pollen-glands were unaffected. Professor Reichenbach also exhibited at the Amsterdam Botanical Congress, of 1865, a flower of Selenipedium caudatum with a flat lip.

M. Gris has placed on record some interesting cases of peloria of this kind in Zingiber zerumbet; in the more complete forms the andrœcium or staminal series was composed of six distinct pieces, the three inner of which were fertile, while in the ordinary flower the andrœcium is composed of two pieces, "a lip" and a fertile stamen. "Is it not a matter of regret," says M. Gris, "to be obliged to call the latter the normal flower?"

Under this head may likewise be mentioned those cases in which the normal, or at least the typical symmetry of the flower is restored by the formation of parts usually suppressed; thus Moquin cites an abnormal flower of Atriplex hortensis described by M. Fenzl as having a true calyx within the two bracts that usually alone encircle the stamens. Adanson, also cited by Moquin, found a specimen of Bocconia with a corolla. Arum maculatum has likewise been met with provided with a genuine perianth as in Acorus and other Orontiads. The unusual development of the sexual organs in diclinous flowers has been alluded to under the head of heterogamy, and other cases where the symmetry of the flower is rendered regular, by the development of parts ordinarily suppressed, will be found in the chapters relating to deviations from the usual number of organs.

This change, or rather this persistence of a form that is usually transient, is generally accompanied by some other alterations. Change of direction, as has been already mentioned, is one of the most common of these; separation of the petals (Antirrhinum, Verbascum, &c.), and even their appearance in leaf-like guise, are not infrequent (Delphinium, Antirrhinum, Verbascum, &c.) At other times multiplication or increased number of the whorls of petals takes place, often, but not always, at the expense of the sexual organs of the flower. Perhaps even more frequent is the increased number of parts in the same whorl in cases of regular peloria; thus, in the Pelargoniums before alluded to, the parts of the flower are frequently regulated by the number six instead of five.

This form of peloria is most generally met with in flowers that are placed at the end or in the centre of the inflorescence, or in such flowers as occur singly at the end of the flower-stalk, as in Tropæolum, Viola, &c. It would hence seem as if the freedom from pressure or restriction on one side allowed the flower to develop equally in all directions, and thus to produce regularity of form.

It is obvious, from what has been before said, that the process of fertilisation is in many cases interfered with and altered by the change in the conformation or the flower.

From overlooking the occasional existence of this form of peloria, new genera have sometimes been formed on insufficient grounds. The genus Aceranthus, for instance, consists of species of Epimedium in which the customary spurs are not formed.

The occurrence both of regular and irregular peloria on the same plant has frequently been observed in Linaria. It has also been remarked that the seedlings raised from these forms are not always constant; thus, the late Mr. Crocker, formerly foreman in the Royal Gardens, Kew, informed me that he fertilised some flowers of a drooping Gloxinia with their own pollen, and that when the seedlings blossomed a large number of them produced the erect regular flowers.

From what has been already said it will be seen that regular peloria is closely allied to what Morren called epanody, or a return to the normal condition. The reversion of a monstrous form to the normal one, as, for instance, when the fern-leaved beech reverts to the normal type, was called by the same author epistrophy.

The following are the genera in which regular peloria has been most often observed. It must, however, be remarked that in some of the flowers recorded as peloric there is no indication as to which form of peloria the case should be referred to. For other illustrations refer to chapters on Heterogamy, Number, Irregular Peloria, &c.

• *Delphinium peregrinum!
• *Nigella damascena!
• *Aquilegia vulgaris!
• *Viola odorata!
• hirta.
• Epimedium, sp.
• *Pelargonium zonale!
• *inquinans!
• Tropæolum majus!
• *Wistaria sinensis.
• Lupinus.
• *Cytisus Laburnum!
• Trifolium repens!
• *Compositæ, gen. pl.!
• Lonicera Periclymenum!
• Streptocarpus Rexii.
• *Digitalis purpurea.
• *Scrophularia aquatica.
• *Pentstemon.
• *Linaria vulgaris!
• *Antirrhinum majus!
• Verbascum nigrum!
• Columnea Schiedeana.
• Halenia heterantha.
• Galeobdolon luteum.
• Prunella vulgaris!
• Salvia, sp.!
• Teucrium campanulatum.
• Betonica alopecuros.
• Eccremocarpus scaber.
• Pedicularis sylvatica.
• Zingiber Zerumbet.
• Phalænopsis amabilis!
• Phalænopsis Schilleriana.
• Habenaria.
• *Orchis morio.
• mascula.
• *Dendrobium, sp.
• Atriplex, sp.
• Cattleya Mossiæ!
• marginata.
• Calanthe vestita!
• Oncidium, sp.!
• Selenipedium caudatum.
• Arum maculatum.

In addition to the references already given, further information on this subject may be gained from consulting the following publications. See also Irregular Peloria.

Giraud, 'Bot. Soc. Edinb.,' Dec. 12, 1839, Antirrhinum. Dareste, 'Ann. Sc. Nat.,' ser. 2, 1842, xviii, p. 220, Delphinium. C. Morren, 'Fuchsia,' p. 90, Calceolaria, 'Bull. Acad. Belg.,' xx, part ii, p. 57; and E. Morren, 'Bull. Acad. Belg.,' 2nd ser., xix. p. 224, Gloxinia. Richard, 'Mém. Soc. d'hist. nat.,' ii, p. 212, tab. 3. Lindley, 'Journ. Linn. Soc.,' iii, p. 9, Dendrobium. Michalet, 'Bull. Soc, Bot. France,' vii, p. 625, Betonica. Gubler, 'Bull. Soc. Bot. Fr.,' ix, 81, 'Des anomalies aberrantes et regularisantes.' Reichenbach fil. 'De pollinis orchid. genesi ac structura,' 1852, Oncidium. Clos, 'Mém. Acad. Toulouse,' vi, 1862, Salvia. Caspary, 'Verhandl. Phys. Œkon. Gesell. Königsberg,' 1860, i, 59, Columnea. Bureau, 'Bull. Soc. Bot. Fr.,' 1861, vol. viii, p. 710, Streptocarpus. Darwin, 'Variation of Animals and Plants,' ii, pp. 59 and 396. Godron, 'Ex. Bull. Bot. Soc. Fr.,' xiv, p. 165, 'Rev. Bibl.,' Wistaria. Marchand, 'Adansonia,' iv, p. 172, Lonicera. Baillon, 'Adansonia,' v, p. 177, 'Sur la regularité transitoire de quelques fleurs irreg.,' shows that during the development of some flowers which begin and end by being irregular, there is an intermediate state when all the parts are regular. Helye, 'Revue Horticole,' Sept., 1868, p. 327. In this last paper, published as this sheet is going through the press, the author states that he has raised from seed three generations of plants of Antirrhinum with regular spur-less flowers. The original wild plant was only partially peloric, but all the flowers produced on its descendants were regular.

Part II. Pleiomorphy.

Most irregular flowers owe their irregularity to an unequal development of some of their organs as compared with that of others. When such flowers become exceptionally regular they do so either because development does not keep pace with growth, and a regular flower is thus the result of an arrest of the former process (regular peloria), or because the comparatively excessive development, which usually occurs in a few parts is, in exceptional cases manifested by all, hence the flower becomes regular from the increase in number of its irregular elements. These latter cases, then, are due to an excess of development, hence the application of the term pleiomorphy. It must be understood that mere increase in the number of the organs of a flower is not included under this head, but under that of deviations from the ordinary number of parts.

Chapter I. Irregular Peloria.

The term peloria was originally given by Linné to a malformation of Linaria vulgaris, with five spurs and five stamens, which was first found in 1742 near Upsal. This was considered so marvellous a circumstance that the term peloria, from the Greek πελωρ, a prodigy, was applied to it. After a time other irregular flowers were found in like condition, and so the term peloria became applied to all cases wherein, on a plant habitually producing irregular flowers, regular ones were formed. The fact that this regularity might arise from two totally different causes was overlooked, or at least not fully recognised, even by Moquin-Tandon himself. Where a flower retains throughout life the same relative size in its parts that it had when those parts first originated the result is, of course, a regular flower, as happens in violets and other plants. This kind of peloria may for distinction sake be called regular or congenital peloria (see chapter on that subject); but where a flower becomes regular by the increase in number of its irregular portions, as in the Linaria already alluded to, where not only one petal is spurred, but all five of them are furnished with such appendages, and which are the result of an irregular development of those organs, the peloria is evidently not congenital, but occurs at a more or less advanced stage of development. To this latter form of peloria it is proposed to give the distinctive epithet of irregular.

Peloria is either complete or incomplete; it is complete when the flower appears perfectly symmetrical, it is incomplete when only a portion of the flower is thus rendered regular. It is very common, for instance, to find violets or Linarias with two or three spurs, and these intermediate stages are very interesting, as they serve to show in what way the irregularity is brought about. In Antirrhinum, Linaria, &c., intermediate forms show very clearly that it is to the repetition of the form usually assumed by the petals of the lower lip that the condition is due. This is also obvious in peloric flowers of the Calceolaria. The perfect peloria of this flower is in general erect, with five regular sepals, a regular corolla contracted at the base and at the apex, but distended in the centre so as to resemble a lady's sleeve, tight at the shoulder and wrist, and puffed in the centre!

Morren describes a form intermediate between the ordinary slipper-shaped corolla and the perfect peloria just described, and which he calls sigmoid peloria. This flower is intermediate in direction between the erect peloria and the ordinary reflected flower. The tube is curved like a swan's neck and is dilated in front into two hollow bosses, such as we see in the lower lip of an ordinary flower; beyond these it is contracted and is prolonged into a slender beak terminating in two hollow teeth, between which is the narrow orifice of the corolla. The colour at the base of the tube inside is as in the perfect peloria; while round the summit of the tube, in both cases, the intensity of colour is greatest on the outside. Now, in a normal flower the deepest colour is within just opposite the orifice of the corolla; this deep colour is also seen outside of the central and most elevated portions of the lower lip. In the peloria the deep colour at the base of the tube represents that which is near the orifice under ordinary circumstances, while the outer patch of colour at the apex corresponds to that formed on the upper surface of the lower lip. On the other hand, in peloric flowers of Cytisus Laburnum, Clitoria Ternatea, Trifolium repens, and other Papilionaceæ, it is the "standard," the form of which is repeated. In the case of peloric aconites the lateral and sometimes the inferior coloured sepals assume the hooded form usually peculiar to the upper sepal only, the number of the petals or nectaries being correspondingly increased. Balsams become peloric by the augmentation in the number of spurs. So when orchids are affected with irregular peloria it is the form of the labellum that is repeated, the accessory lips being sometimes the representatives of stamens, which are usually suppressed in these flowers, but at other times the appearance is due simply to the fact that all three petals assume the form usually confined to the lip, the staminal column being unaffected, except that its direction and relative position with reference to the other parts of the flower is different from ordinary. This was the case in some flowers of Phalænopsis equestris sent to me by Mr. Wentworth Buller. Fig. 123 represents a flower of Aristolochia caudata with two lips, for which I am indebted to Mr. W. H. Baxter.

From these cases it is evident that the flowers in question become regular by the repetition of the irregular parts.

It is probable that peloria may occur in any habitually irregular flower, and that, if more attention were directed to the subject, illustrations might be obtained from a larger number of natural families than can be done at present. It is, however, necessary to exercise discrimination, and not to attribute to peloria all the cases that at first sight appear to be so referable. Thus, Professor Dickson exhibited at the Botanical Society of Edinburgh, December 13th, 1860, four abnormal flowers of the common Indian cress (Tropæolum majus), each presenting a supernumerary spur. On these he remarked that "in Tropæolum the posterior part of the receptacle between the insertion of the petals and that of the stamens is dilated so as to form the spur which is so characteristic in the genus. The position of the spur in a line with the posterior sepal has led many botanists to consider it as a process of that sepal, but the fact of its being situated within the insertion of the petals is conclusive as to its receptacular origin. In the flowers exhibited the supernumerary spur (as if to show its want of connection with any sepal) was placed exactly between a lateral sepal and one of the anterior sepals, sometimes on the one side of the flower and sometimes on the other. These additional spurs were precisely similar to the normal ones, except that they were a little shorter. This abnormality, although at first sight seeming to indicate a pelorian tendency, is no approximation to regularity, from the fact of the extra spur being differently placed, with regard to the sepals, from the normal one."

Peloria of this kind, when perfect, is very often associated with other alterations. Change of direction is one of the most common of these; the usually drooping flower becomes erect, the stamens and style also are changed in direction, while, not unfrequently, either the one or the other (most often the stamens) are entirely suppressed. With this suppression an increase in the size of the flower very generally coincides. The number of parts is also frequently increased; thus, in Antirrhinum majus the corolla, when subjected to peloria, is very generally six-parted, and has six stamens. Fusion of one or more flowers is also a common accompaniment of peloria, as in Digitalis purpurea, in which plant prolification often adds increased complexity to the flower.

It has been stated by Moquin and others that the uppermost flower of an inflorescence is the most subject to peloria; the uppermost flower of Teucrium campanulatum, for instance, is very generally regular. In Calceolaria it is the central terminal flower which is usually peloriated; on the other hand, in Linaria and Antirrhinum the lower flowers, or those on the secondary branches, are quite as often affected as the primary ones. Cassini considered that the spur of Linaria was developed from the lower petal rather than from the upper ones, because there is more room on the side of the flower farthest from the stem than on the opposite side. With reference to this point, M. Godron remarks that in habitually irregular flowers the apex of the peduncle is oblique, and hence the flowers are bent downwards or spread horizontally, but if the receptacle be quite flat and level then the flower is regular. The oblique position causes some of the organs to press on others, and hence induces abortion and suppression of some parts and increased growth in others that are not subjected to pressure. In a terminal peloriated flower of aconite, described by this naturalist, the flower was removed so far from the nearest bracts that all its parts had the chance of growing regularly. In ordinary cases M. Godron considers that the compression of the lateral bracts is the cause of the irregularity of the andrœcium and of the receptacle.

It has also been somewhat too generally stated that peloria occurs principally on luxuriant vigorous plants. It seems quite as often to happen in plants characterised by their deficiencies in this respect. On this point M. de Melicoq says, referring to Linaria vulgaris affected with peloria, that on the weakest plants the peloriated flower was at the top of the stem; while in stronger plants, with more numerous flowers and larger foliage, the peloriated flowers were principally to be found in the centre and at the base of the inflorescence, and their pedicels were much longer than usual.

Linné, as has been already stated, considered these flowers to be sterile, and only capable of multiplication by division of the root, but Willdenow obtained seeds from the Linaria which reproduced the anomaly when sown in rich soil. Baron Melicoq obtained similar results. Mr. Darwin raised sixteen seedling plants of a peloric Antirrhinum, artificially fertilised by its own pollen, all of which were as perfectly peloric as the parent plant. On the other hand, the same observer alludes to the tendency that these peloric plants have to revert to the usual form, as shown by the fact that when the peloric flowers were crossed with pollen from flowers of the ordinary shape, and vice versâ, not one of the seedlings, in either case, bore peloric flowers. Hence, says Mr. Darwin, there is in these flowers "a strong latent tendency to become peloric, and there is also a still greater tendency in all peloric plants to reacquire their normal irregular structure." So that there are two opposed latent tendencies in the same plant. A similar remark has been made with reference to malformations in general by other observers.

It would be very interesting if some competent naturalist would collect information as to whether any variations in degree of fertility exist in the three forms of flowers in Linaria, viz. the ordinary one-spurred form, which is intermediate between the spur-less and the five-spurred form. It must be remembered, however, that in the latter cases the stamens are often deficient. In the Compositæ, where there are regular flowers in the disc and irregular ones in the ray, sexual differences, as is well known, accompany the diversities in form.

To Mr. Darwin the author is indebted for the communication of some flowers of Corydalis tuberosa (figs. 124, 125), provided with two spurs of nearly equal size. To these flowers allusion is made in the work already quoted in the following terms:—"Corydalis tuberosa properly has one of its two nectaries colourless, destitute of nectar, only half the size of the other, and therefore to a certain extent in a rudimentary state; the pistil is curved towards the perfect nectary, and the hood formed of the inner petals slips off the pistil and stamens in one direction alone, so that when a bee sucks the perfect nectary the stigma and stamens are exposed and rubbed against the insect's body. In several closely allied genera, as in Dielytra, there are two perfect nectaries; the pistil is straight, and the hood slips off on either side, according as the bee sucks either nectary." In the flowers of Corydalis, which were provided with two perfect nectaries containing nectar, Mr. Darwin considers that there has been a redevelopment of a partially aborted organ, accompanied by a change in the direction of the pistil, which becomes straight, while the hood formed by the petals slips off in either direction, "so that these flowers have acquired the perfect structure, so well adapted for insect agency, of Dielytra and its allies."

Peloria, then, is especially interesting physiologically as well as morphologically; it is also of value in a systematic point of view, as showing how closely the deviations from the ordinary form of one plant represent the ordinary condition of another; thus, the peloric Calceolarias resemble the flowers of Fabiana, and De Candolle, comparing the peloric flowers of Scrophulariaceæ with those of Solanaceæ, concluded that the former natural order was only an habitual alteration from the type of the latter. Peloric flowers of Papilionaceæ in this way are indistinguishable from those of Rosaceæ. In like manner we may trace an analogy between the normal one-spurred Delphinium and the five-spurred columbine (Aquilegia), an analogy strengthened by such a case as that of the five-spurred flower of Delphinium elatum described by Godron. The Corydalis, before referred to, is another illustration of the same fact, the structure being the same as in Dielytra, &c.

The ordinary irregular flowers may possibly be degenerated descendants of a more completely organized ancestor, and some of the cases of peloria may therefore be instances of reversion; some ancient Linaria may, perhaps, have had all its petals spur-shaped, and the cases of irregular peloria now found may be reversions to that original form. When both regular and irregular forms of peloria occur on the same plant, as they frequently do in Linaria, the one may be perhaps considered as a reversion to a very early condition, the other to a later state, when all the petals were irregularly formed. But before we can assert the truth of this surmise we must have better evidence as to what the original condition really was than we have at present.

The proximate cause of irregular peloria has been considered to be excess of nourishment, but evidence as to this point is very conflicting. Willdenow states that "radices peloriæ, solo sterili plantatæ, degenerant in Linariam," ('Sp. Plant.,' iii, p. 254); but this opinion is counterbalanced by that of others, while the frequent existence of both forms on the same plant, at the same time, seems to negative the supposition of any direct effect from external circumstances.

The following are the plants in which irregular peloria has been most often observed:

• Aconitum Napellus.
• Delphinium elatum!
• Corydalis tuberosa.
• *Viola odorata!
• hirta.
• Impatiens Balsamina.
• Clitoria Ternatea.
• Cytisus Laburnum!
• Trifolium repens!
• Lupinus polyphyllus!
• *Gloxinia, var. cult.!
• *Linaria vulgaris!
• spuria.
• Elatine.
• triphylla.
• æruginea.
• triornithophora.
• pilosa.
• chalepensis.
• cymbalaria!
• purpurea!
• decumbens.
• Pelisseriana.
• origanifolia.
• Digitalis orientalis.
• *purpurea!
• Calceolaria crenatiflora.
• rugosa.
• *var. cult.!
• Chelone barbata.
• *Antirrhinum majus!
• Rhinanthus crista galli.
• Pedicularis sylvatica.
• Pedicularis euphrasioides.
• Scrophularia aquatica!
• Sesamum indicum.
• Lamium.
• Mentha.
• Sideritis.
• Nepeta diffusa.
• Galeopsis Ladanum.
• Tetrahit.
• Galeobdolon luteum.
• Teucrium campanulatum!
• Plectranthus fruticosus.
• Cleonia lusitanica.
• Dracocephalum austriacum.
• Phlomis fruticosa!
• Vitex incisa.
• Aristolochia, sp.!
• Ophrys aranifera!
• Orchis simia.
• pyramidalis!
• latifolia!
• morio!
• papilionacea.
• mascula.
• latiflora.
• conopsea.
• Habenaria bifolia.
• Corallorhiza innata.
• Aceras anthropophora.
• Cattleya Moasiæ!
• Phalænopsis equestris!
• Pogonia ophioglossoides!

The literature of peloria is very extensive. The following are the principal papers, not already mentioned, which relate to the subject, arranged under the genera, placing those first which are most subject to this anomaly (see also Regular Peloria).

Linaria.—Adanson, 'Fam. Plant.,' t. i, p. 110. Jussien, 'Gen. Plant.,' p. 120. Poiret, 'Encycl. Method, Suppl.,' t. iii, Jaeger, 'Missbilld. der Gewachs.,' pp. 94, 97, and 313. Cassini, 'Op. Phytol.,' t. ii, p. 331. Ratzebourg, 'Animadv. ad pelor. spectand.,' 1825. Turpin. 'Ic. Veget.,' tab. xx, f. 16. Curtis, 'Flor. Londin.,' i, 118. Hopkirk, 'Flora Anom.,' pl. vii, figs. 1, 2, 3. Haller, 'Act. Helvet.,' 2, p. 25, t. iv. De Candolle, 'Flore Franc.,' t. iii, p. 583. Sowerby, 'Engl. Bot.,' iv, 260, ed. Syme, tab. 963. Chavannes, 'Mon. Antirrhin.' Delavaud, 'Bull. Soc. Bot. France,' 1858, p. 689; id., 1860, p. 175. Heufler, 'Linnæa,' xvii, tab. ii. Weber, 'Verhandl. des Nat. Hist. Vereins. f. d. Rh. Preuss.,' 1850, tab. i, figs. 1–8. 'Verh. Nat. Hist. Ver. Rh. Preus.,' 1849, vol. vi, p. 290, tab. xiii.—Antirrhinum, Clos, 'Mém. Acad. Toulous.,' vi, 1862. Chavannes, 'Mon. Antirrh.,' p. 62. Fresenius, 'Mus. Senkenb.,' ii, t. iv, fig. 10. 'Bot. Soc. Edinb.,' 1851, July 10.—Calceolaria, Chamisso, 'Linnæa,' t. vii, p. 206. Guillemin, 'Archiv. Bot.,' t. ii, p. 1 et 136. Schlechtendal, 'Linnæa,' xii, p. 686. Ernst Meyer, 'Linnæa,' xvi, 26, tab. iii. Morren, 'Bull. Acad. Belg.,' t. xv, n. 7, et t. xviii, p. 583. 'Gard. Chron.,' 1850, p. 389; ibid., 1866, p. 612.—Viola, Leers, 'Flor. Herborn.,' p. 145. De Candolle, 'Organ. Veget.,' t. i, p. 519, pl. xlv. Forbes, 'Proc. Linn. Soc.,' June 6, 1848, p. 382. Hildebrand, 'Bot. Zeit.,' 1862, vol. xx, tab. viii.—Orchidaceæ, His, 'Jourl. Phys.,' 65, p. 241. Wydler, 'Arch. Bot.,' t. ii, p. 310, tab. xvi. R. Brown, 'Obs. organ. Orchid.,' p. 698. A. Richard, 'Mém. soc. d'hist. nat.,' t. i, p. 212. Greville, 'Flora Edinens.,' p. 87 (Corallorhiza). Curtis, 'Flora Londinensis,' t. lxxxii. Morren, C., 'Bull. Acad. Roy. Belg.,' t. xix, part ii, p. 171. Clos, 'Mém. Acad. Sc. Toulous.,' 5 ser., vol. iii. Caspary, 'Schrift. K. Gesellsch. Königsberg,' 1860, i, 59. Masters, 'Jourl. Linn. Soc.,' vol. viii, p. 208 (Ophrys, Pogonia). Duchartre, 'Bull. Soc. Bot. Fr.,' vol. vii, 1860, p. 26, Cattleya. Cramer, 'Bildungsabweich.'—Limosella, Baillon, 'Adansonia,' i, p. 305. (Flower normally irregular, becoming regular "à force d'irregularité.")—Chelone, Chamisso, 'Linnæa,' vii, p. 206,—Clitoria, Bonavia, 'Gard. Chron.,' 1868, p. 1013. In this latter communication, published as this sheet is passing through the press, the author gives an interesting account of the transitional stages between the ordinary papilionaceous condition and the regular form which is like that of a Rosaceous plant. The peloric form is stated to be transmitted by seed.

For other references see Moq.-Tandon, 'El. Terat. Veget.,' p. 186. Hallier, 'Phytopathol.,' p. 151.

Part III. Metamorphy.

Much of the objection with which Goethe's famous essay on the 'Metamorphosis of Plants' was met on its publication may be traced to a misapprehension of the sense in which Goethe employed the word. As used by him, it had nearly the same signification as now applied to the word development by organogenists. It does not necessarily imply that there has been a change in any particular organ, but rather that there has been, to some extent, a change in the plan of construction, in accordance with which a deviation from the customary form results. The particular organ was never anything else than what it is; it has not been metamorphosed in the ordinary sense of the word; for instance, in a double flower, where the stamens are, as it is said, changed or metamorphosed into petals, no absolute change really has taken place—the petal was never a stamen, although it occupies the position of the latter, and may be considered a substitute for it.

The term metamorphosis, then, really implies an alteration in the organizing force, taking effect at a very early period of the life of the flower, at or before the period when the primitive aggregation of cells, of which it is at that time composed, becomes separated or "differentiated" into the several parts of the flower. In other words, the "development" of the flower pursues a different course from what is usual. In the preceding sections the effects of arrest and of excess in this process have been partly treated of; other deviations arising from similar causes will be mentioned elsewhere, but, under the present heading, are specially included cases not of merely diminished or increased, but of perverted development; the natural process is here not necessarily checked or enhanced, but it is changed. Hence, in the present work, the term metamorphy is employed to distinguish cases where the ordinary course of development has been perverted or changed. As it is applied solely for teratological purposes, the ordinary acceptation of the term, as nearly synonymous with "development," is not interfered with.

In order to avoid other possible misapprehensions, the terms retrograde and progressive metamorphosis employed by Goethe are not herein used, their place being, to a great extent, supplied by the more intelligible expressions arrest or excess of development.

Chapter I. Phyllody.

This condition, wherein true leaves are substituted for some other organs, must be distinguished from Virescence, q. v., in which the parts affected have simply the green colour of leaves, without their form or structure. The appearance of perfect leaves, in place of other organs, is frequently looked on as due to retrograde metamorphosis, or to an arrest of development. But this is not strictly correct; for instance, suppose a petal, which is very generally merely the sheath of a leaf, with the addition of colouring matter, to be replaced by a perfect leaf, one in which all three constituent parts, sheath, stalk, and blade, are present, it surely can hardly be said that there has been any retrogression or arrest of development in the formation of a complete in place of an incomplete organ. The term retrograde here is used in a purely theoretical sense, and cannot be held to imply any actual degradation. Morphologically, as has been stated, the case is one of advance rather than the reverse, and hence the assignment of instances of this nature to a perversion of development, rather than to a diminution or to an exaltation of that process, seems most consistent with truth. The affected organs have really undergone no actual change, simply the direction of the organising force has been altered at a very early state, so that the usual differentiation of parts has not taken place.

Phyllody of the bracts.—As bracts are very generally imperfect organs, so their replacement by perfect leaves is not attributable to arrest of development or retrograde metamorphosis, but the reverse. The bracts of some species of Plantago are very subject to this change. Thus, in the rose plantain of gardens, P. media (fig. 126), the bracts are leafy and the axis depressed or not elongated, so that it is surmounted by a rosette of small leafy organs. A similar condition of the bracts, unattended with arrest of growth in the axis, is common in P. major (fig. 127) and in P. lanceolata (see p. 108). It also occurs in the bracts of Corydalis solida, Amorpha fruticosa, Ajuga reptans, Parthenium inodorum, Centaurea Jacea, in the involucral bracts of the dandelion, the daisy, and many other composites. In the 'Gardeners Chronicle,' 1852, p. 579, is figured a dahlia in which the bracts of the involucre and the scales of the receptacle had all assumed the form, texture, and venation of leaves.

In Umbelliferæ the substitution of leaves for involucral bracts is not infrequent. It has been observed among other plants in Angelica Razoulzii, Carum carui, Daucus Carota, &c. The scales of the hop (Humulus Lupulus) not infrequently manifest this change, as do also the bracts of many amentaceous plants, e.g. in the male catkins of the walnut, the female catkins of the alder, of some willows, &c. The bracts of some Euphorbiaceæ, as E. pusilla, E. Lathyris, E. Cyparissias, have been observed to undergo a similar alteration.

Amongst monocotyledons an analogous change occurs not unfrequently, as in some commelynaceous plants, e.g. Tradescantia, in Musa, &c.

The spathe of Arum maculatum is sometimes represented by a stalked leaf similar to that which occurs, under ordinary circumstances, in Spathiphyllum, but in which genus the spadix is more or less adherent to the leaf-like spathe. In Schœnus cephalotes a similar exaggerated development of the bracts is figured by Rottboell.

Phyllody in inflorescence of Conifers.—This demands passing notice by reason of the interest attaching to the morphological construction of these plants. The elongation of the axis which occurs in the female cones has been already alluded to under the head of prolification of the inflorescence. This change is frequently associated with a more or less foliaceous condition of the bracts, which, indeed, may be seen to be serially continuous, both above and below, with the ordinary leaves. The scales, too, become notched and bipartite, and show, between the lobes, the rudiment of a bud, which in a further stage becomes developed into a shoot bearing leaves. Such a change has been described by Parlatore in Abies Brunoniana, and examples may frequently be met with in the larch (Larix europæa), and specially in Cryptomeria japonica. The scales of the male catkins of conifers likewise occasionally assume the appearance of leaves; this may be seen in monstrous catkins of Araucaria, as also in Podocarpeæ and Cupressineæ (Eichler).

Phyllody of the calyx.—Sepals under ordinary circumstances are so like leaves, that it is not wonderful that they are often replaced by those organs. A singular instance of this has been mentioned as occurring in Cakile maritima, wherein the sepals were found by M. Fournier to be pinnatifid like the ordinary leaves of the plant. The sepals of Ranunculaceæ and Rosaceæ, for example, Rosa, Geum, are particularly liable to this change.

In a species of Geranium recently examined the sepals presented themselves in the form of three-lobed leaflets; so in fuchsias and in Epilobium hirsutum the sepals occasionally are not distinguishable from ordinary leaves (fig. 130). In roses, the change in question is a very frequent accompaniment of prolification (fig. 129). In the peach also this replacement of the sepals is sometimes carried to such an extent, that five perfect, bistipulate leaves occur in the place of the calyx, but when this is the case it usually happens that the pistil is abortive.

De Candolle figures a curious instance wherein the pappus of Podospermum laciniatum was replaced by five linear, foliaceous lobes. A similar change has been noticed in other composites, as in Tragopogon pratense. Engelmann mentions as subject to this hypertrophy of the pappus, as it may be termed, Scorzonera octangularis and Senecio vulgaris. Wigand has observed a similar transformation in a species of Centranthus (Valerianaceæ).

In some cases the phyllody of the sepals has a special interest, as bearing on the question whether what is termed calyx-tube is or is not a portion of the calyx, and whether the sepals are modifications of the blade or of the sheath of the leaf. Thus in the primrose the phyllodic sepals seem to show clearly that the sepals are in that plant of a laminar nature (fig. 131). The so-called calyx-tube of roses is elsewhere alluded to. The leaf-like organs sometimes seen at the apex of a cucumber would seem to support the view that there was really a calyx-tube in Cucurbitaceæ adherent to the carpels. It is also shown in the cut, fig. 132, borrowed from the 'Gardeners' Chronicle,' 1859, p. 654.

Under ordinary circumstances, the sepals may be considered as the representatives of the sheath of the leaf (cataphyllary) or of the blade (euphyllary), the arrangement of the veins being different in the two cases; thus, in the vagina or sheath, there are generally several large veins of about equal size, either convergent towards the apex, or divergent; on the other hand, in the blade, there is usually but one central vein, the midrib, larger than the rest, and the smaller veins come off at a less acute angle, and are more reticulated.

Now, when phyllomorphy occurs in sepals which ordinarily are vaginal, it is obvious that the case is one, not merely of increased relative growth, but also of the appearance or development of an organ habitually suppressed; on the other hand, when phyllomorphy occurs in sepals which usually are laminar in form and nervation, the case is one of unusual growth or hypertrophy, and not of the development of an organ habitually suppressed, so that the amount of change is greater in the former than in the latter instance.

Under normal circumstances it will be found that laminar venation is most common in gamosepalous and vaginal venation in polysepalous calyces. And the same holds good in cases where the calyx is abnormally leafy. The complete leaf development shows itself more frequently among the monosepalous plants than in the polysepalous ones, as shown even in the subjoined list of species. This statement would be more fully verified were it possible to state the frequency with which the condition occurred in individual plants, when it would be found that phyllody of the calyx occurs much more often in individual gamosepalous plants than in polysepalous ones.

Phyllody of the calyx has been most often observed in the following plants:

• Ranunculus acris!
• Delphinium Ajacis.
• Caltha palustris.
• Anemone Pulsatilla.
• sylvestris!
• nemorosa!
• hortensis!
• coronaria!
• *Papaver orientale.
• Escholtzia crocea.
• Cakile maritima.
• Diplotaxis tenuifolia.
• Thlaspi arvense.
• Cheiranthus Cheiri.
• incanus.
• Sinapis arvensis.
• Brassica oleracea!
• Peltaria alliacea.
• *Sisymbrium officinale.
• Caryophyllaceæ, sp. pl.
• Geranium, sp.!
• *Fuchsia, var. hort.!
• Epilobium hirsutum!
• Cucurbita Pepo!
• *Rosa, var. hort.!
• Potentilla nepalensis.
• Fragaria sp.
• Geum rivale.
• Amygdalus communis.
• Persica vulgaris.
• Cerasus!
• Pyrus Malus.
• Daucus Carota.
• Athamanta Cervaria.
• *Trifolium repens!
• Centranthus macrosiphon.
• Tragopogon pratense.
• orientale.
• Scorzonera octangularis.
• Hypochæris radicata.
• *Senecio vulgaris!
• Podospermum laciniatum.
• Cirsium arvense.
• Carduus heterophyllus
• tataricus.
• Campanula, sp.
• Convolvulus sepium.
• *Primula officinalis, var. cult!
• acaulis.
• elatior.
• Gentiana campestris.
• *Petunia violacea!
• Lycium europæum.
• Laurus Sassafras.
• Tulipa Gesneriana.
• Convallaria maialis.
• Colchicum autumnale! (virescent?)

Consult also Turpin, 'Atlas de Goethe,' t. iv, f. 12, Lycium. Engelmann, 'De Anthol.,' § 35, p. 31. This author figures phyllodic sepals in Senecio vulgaris, tab. v, figs. 24–26; Campanula, tab. iii, f. 15, 16; Athamanta cervaria, tab. v, f. 14. Lindley, 'Elements of Botany,' 1847, pp. 64, 73, &c. 'Gard. Chron.,' 1858, p. 685; 1859, p. 654, Cucurbita. Petunnikoff, 'Bull. Soc. Imp. Moscow,' 1862, Cirsium. Braun, 'Rejuvenescence,' Ray Society's Transl. See succeeding paragraphs.

Phyllody of the corolla.—The petals also are frequently replaced by leaves, though in many of the recorded instances the change has been one of colour only; these latter are strictly cases of virescence. M. Seringe speaks of a flower of Peltaria alliacea in which the calyx was petal-like, while the corolla was leafy as if there had been transposition of the two organs, a very rare, if not unparalleled, instance. In a flower of Campanula Medium, provided, as is often the case, with a double corolla, the outer corolla was slit down on one side, the edges of the cleft being leafy.

The frondescent petals are very often completely disjoined, as in Verbascum nigrum, and Lonicera Periclymenum, in which, moreover, median prolification generally coexists. In the case of Tropæolum majus, the ordinary leaves of which are peltate and orbicular, the petals when frondescent have not the peltate arrangement, but are spathulate, and provided with very long, narrow stalks, so that, in some cases, they are, more properly speaking, enlarged virescent petals than true leaves; in other instances, however, the arrangement of the veins is more like that of the true leaves than that of the petals.

As might be expected, frondescence of the petals is frequently accompanied by other changes of a similar nature in other parts of the flower, and sometimes by the abortion of the sexual organs. Thus, in Actæa spicata, as observed by Fresenius, the petals were replaced by true petiolate, palminerved, lobed leaves, the stamens and pistils being abortive. In Ranunculus the leaves that appear in the place of the petals have no scale at their base, and in Tropæolum the calyx (or receptacle) is free from the usual spur.

The absolute frequency of this occurrence seems to be greatest in those flowers which are normally polypetalous. The petals of these flowers, as a general rule, are more like the leaf-sheaths than the leaf-blades as to their venation, hence it would seem that the phyllomorphic condition in these petals is a manifestation of a greater degree of organizing force than that which occurs in those cases where the petals are normally present in the form of contracted blades or laminæ. (See the remarks in the preceding section.)

Frondescence of the petals has been observed most frequently in the following cases; some, perhaps, were cases merely of virescence, q. v.; see also under Chloranthy, Prolification.

• Ranunculus repens!
• Delphinium Ajacis.
• crassicaule.
• Aquilegia vulgaris.
• Actæa spicata.
• *Brassica oleracea!
• Diplotaxis muralis.
• Hesperis matronalis.
• Thlaspi bursa pastoris.
• Sisymbrium tenuifolium.
• Turritis glabra.
• Raphanus sativus.
• Peltaria alliacea.
• Alyssum incanum.
• Erysimum Barbarea.
• officinale!
• cheiranthoides.
• Cheiranthus Cheiri.
• *Dictamnus Fraxinella!
• Lychnis sylvestris.
• dioica!
• Alsine media.
• Cerastium vulgatum!
• triviale.
• Reseda lutea.
• Phyteuma.
• Malva sylvestris.
• *Tropæolum majus!
• Geranium, sp.!
• Triumfetta, sp.!
• Epilobium hirsutum!
• Œnothera striata.
• Rubus, sp.
• *Rosa, var. cult.!
• *Trifolium repens!
• Spiræa oblongifolia.
• Amygdalus communis.
• *Rosa!
• Cerasus vulgaris!
• Persica vulgaris!
• Potentilla nepalensis.
• Geum rivale.
• Daucus Carota!
• Heracleum Sphondylium.
• Torilis Anthriscus.
• Echinophora maritima.
• Campanula rapunculoides.
• glomerata.
• Phyteuma spicatum.
• Calendula officinalis.
• Cirsium tricephalodes.
• Senecio vulgaris.
• Scabiosa columbaria.
• agrestis.
• Lonicera xylosteum.
• Periclymenum.
• Gentiana Amarella.
• Gilia glomeriflora.
• *Symphytum officinale.
• Petunia violacea!
• Verbascum, sp.
• Antirrhinum majus!
• Stachys sylvatica.
• *Anagallis phœnicea?
• Primula sinensis!
• Polemonium cœruleum.

See Moquin-Tandon, 'El. Terat. Veg.,' p. 203. Engelmann, 'De Anthol.,' § 38 et seq.; tab. ii, figs. 8–14, Gilia; tab. v, 23–26, Senecio; tab. v, f. 1–13, Torilis; tab. iv, f. 3, Erysimum. 'Bull. Soc. Bot. Fr.,' vol. ii, 1855, p. 479, Primula sinensis. Giraud, 'Edinb. Phil. Magazine,' 1839, Antirrhinum. Jaeger, 'Act. Acad. Cæs. Nat. Cur.,' vol. xiii, 2, p. 1, tab. xli, Tropæolum. Bischoff, 'Lehrbuch,' 11, 2, p. 27, note, Tropæolum. Fresenius, 'Mus. Senkenb.,' ii, 35, tab. 4, fig. 5, Actæa. See also succeeding paragraphs and sections in Chloranthy, Virescence, &c.

Phyllody of the stamens happens less frequently than the corresponding condition in the neighbouring organs. The structure of the anther is so much removed from that of the leaf, that the change of the stamen from its ordinary condition to that of a leaf must be regarded as indicating a greater degree of perverted development than that which occurs in those cases where less highly differentiated organs, such as the sepals, petals, and pistils, are thus altered.

In all cases it is desirable to ascertain, if possible, what parts of the stamen are thus transformed. In some Petunias the filaments are unchanged, but in place of the anther is a small lamina, representing precisely the blade of an ordinary leaf. Sometimes the connective only is replaced by a leaf. One of the most interesting cases of this kind that has fallen under the writer's observation was in Euphorbia geniculata, in which, in addition to other changes mentioned under prolification of the inflorescence, some of the stamens were partly frondescent, half the anther being perfect, the other half leaf-like. Another filament bore just above the usual joint three leaflets, two lateral ones, somewhat conduplicate, and a third central one, half anther, half leaflet.

In the case of frondescent flowers of Tropæolum majus the stamens are usually absent or atrophied, but in other instances the filament is present as usual, representing the stalk of the leaf, and surmounted by a small lamina, but this latter, in place of being nearly flat, is pinched up in the centre from back to front, and surmounted by a two-lobed anther, so that the general appearance of the whole structure is that of a central anther, supported at the base on each side by two concave leaf-lobes, or it might be compared with a three-lobed leaf, the terminal lobe represented by the anther.

In Jatropha Pohliana, Müll. (Adenorophium luxurians, Pohl.), a singular condition has been observed by M. Müller (Argov.). In this flower the anther, in place of being represented by the flat blade of a single leaf, had the appearance as if two such blades were present and coherent one with the other by their midribs, along their upper or inner surfaces, which were directed towards the centre of the flower (fig. 136), thus resembling the cases of adhesion of leaves by their surfaces already referred to (p. 33). In other cases, in the same plant, the anther appeared as if formed by two collateral leaves, the faces looking towards the circumference of the flower, and their margins so folded together as to represent an open anther lobe (fig. 135). These cases are apparently due, not to the formation and adhesion of two leaves, but rather to the exuberant development of one leaf into two blades. The bearings of these and other similar malformations on the morphology of the anther are alluded to under the head of petalody of the anther.

Phyllody of the stamens has been most often observed in the following plants:

• Anemone nemorosa.
• coronaria.
• Delphinium crassicaule.
• Nymphæa dentata.
• Tropæolum majus!
• Dictamnus albus.
• *Trifolium repens!
• Torilis anthriscus.
• Heracleum Sphondylium.
• Daucus Carota
• Epilobium hirsutum!
• *Rosa, var. cult.!
• Lonicera Periclymenum.
• Anagallis arvensis.
• Primula sinensis!
• Petunia, var. cult.
• Jatropha Pohliana.
• Euphorbia goniculata.

In addition to the foregoing there are very numerous instances of similar substitution in chloranthic flowers. In the above list only those cases are given wherein the leafy change is confined to the stamens, or, at least, to a few only of the other parts of the flower.

Phyllody of the pistils.—This is of more common occurrence than is the corresponding change in the case of the stamens. It is of interest, as it sometimes serves to illustrate the morphological nature of the pistil. Of this the double-flowering cherry is a well-known illustration, the pistil being here represented by two small foliar laminæ, whose midribs are prolonged with a short style, terminated by an imperfect stigma. It is usually the basal portion of the pistil, the ovary, which is thus specially affected, the margins being also often disunited so as to expose the ovules. These latter organs may be absent or they may themselves be the subjects of foliaceous development. Moquin relates having found in the neighbourhood of Montpellier a flower of a tulip the ovary of which was represented by true leaves, which bore on their margins the ovules, and thus presented a striking analogy with the carpels of those Sterculias, like S. platanifolia, which are foliaceous in texture and open very early in the course of their development. A similar occurrence has also been frequently noticed in the Columbine and also in Cruciferæ and Umbelliferæ. M. Germain de St. Pierre mentions an instance wherein the carpels of Salix Babylonica were converted into two leaves, provided with stipules. All the flowers of the catkins were similarly changed, so that it became permanent, and resembled a branch.

Substitutions of this kind form the green "eyes" or centres of certain varieties of Ranunculus and Anemone.

In proliferous roses, or in cases where the central axis of the flower is prolonged, it frequently happens that the pistils are more or less replaced by leaves. Fig. 137, from a specimen of Dr. Bell Salter's, given in the 'Gardeners' Chronicle,' shows the passage, from below upwards, of the ordinary carpels to perfect leaves; the so-called calyx-tube being completely deficient and the ovaries entirely superior. Like most similar specimens, this one bears out the notion that what is called the calyx-tube in roses is really an expansion and dilatation of the top of the flower-stalk.

Fig. 138, for which I am indebted to Mr. S. J. Salter, represents a very singular conformation in the cucumber, described by that gentleman in 'Henfrey's Botanical Gazette,' i, p. 208, and considered by him to be due to the foliaceous condition of one of the three carpels of which the fruit is composed. The portion near the peduncle was binary, while the distal extremity of the fruit was ternary. The main difficulties attending the acceptance of this explanation reside in the peculiar reversed position of the leaf, and in the fact that the fruit of the Cucurbitaceæ is probably of axial nature, the dilated and succulent end of the peduncle adhering to and usually concealing the carpels; in some cases, however, these latter project beyond the axial portion, leaving no doubt as to the true nature of the structure in these particular instances.

Admitting the axial nature of the fruit, it might be supposed that in Mr. Salter's cucumber an adventitious leaf had been given off from the axis, but even on that supposition the reversed position offers a difficulty, and there still remains to be explained the fact that the proximal part of the fruit was binary in its constitution, the distal end ternary.

M. Norman mentions a case wherein the carpels of Anchusa ochroleuca were replaced by two leaves; from this he draws the inference that the pistil of borages and labiates is really composed of two leaves, placed fore and aft, the margins of the leaves being congenitally fused. This tallies well with the account given of the development of these plants by Payer, Germain de St. Pierre, and others.

In an Indian species of Triumfetta, not only were the petals virescent, but the ovary also was much enlarged, and in some flowers it was divided half way down into five lanceolate leaves (fig. 139), the sepals and stamens being in their normal condition.

In the preceding instances the foliaceous condition has pervaded the entire pistil, or at any rate the basal portion or ovary, and it may be noticed that the ovary is thus shown to consist in some cases of the sheath of the leaf, as in Aquilegia; in other cases of the blade, as in Cerasus, Daucus, &c.

There are cases, however, in which a part only of the pistillary structure thus becomes foliaceous. Linnæus, 'Prolepsis,' § 9, mentions some flowers of Carduus heterophyllus and C. tataricus in which the style had grown into two green leaflets, and in which the calyx and corolla were also leaf-like. A very singular instance is recorded by Baillon, wherein the pistil of Trifolium repens consisted of three carpels, either separate, or combined so as to form a one-celled ovary with three parietal, pluri-ovulate placentæ; the ovary in these flowers was formed of the basal vaginiform part of the leaf; the three styles were formed by the petioles, while the stigmas were represented by trifoliolate leaves. The back of the leaf in these cases is usually directed away from the centre of the flower. When this change occurs it is commonly attended by an increased number of parts, as in the trefoil just mentioned, or in the double cherry, where usually two foliaceous carpels may be met with, and sometimes more.

The change is also of interest when it affects such orders as the Umbelliferæ, which have their ovaries inferior under ordinary circumstances; but when these organs assume a leafy condition they become superior also, i.e. they are detached from the calyx.

As regards the position of the ovules in these foliaceous pistils, they may be placed, as in Aquilegia, Delphinium, &c., on the edges of the carpel or on the surface, as in some flowers of Ranunculus repens and R. Ficaria. A similar position of the ovules is recorded in the case of the vine (Vitis), where the pistil consisted of leaves bearing the ovules on their inner surface. The supposed causes of this and other similar malformations are alluded to under the head of chloranthy, but it may be here remarked that semi-double flowers, fertilised by the pollen of similar flowers, are said to produce flowers with a centre of small green leaves, this central tuft resulting from the expansion and frondescence of the pistils.

As this condition rarely occurs without corresponding changes in other parts of the flower, further remarks on this subject will be found in the chapter relating to Chloranthy.

Phyllody of the pistil has been most frequently recorded in the following plants:

• Pæonia officinalis.
• Ranunculus repens!
• *Aquilegia vulgaris!
• Delphinium elatum.
• crassicaule.
• Ajacis.
• amænum.
• Nymphæa dentata.
• Sinapis arvensis!
• Diplotaxis tenuifolia.
• *Brassica oleracea!
• *Sisymbrium officinale!
• Dianthus. sp
• Reseda Phyteuma.
• Triumfetta, sp.!
• Lychnis dioica.
• Cerastium, sp.!
• *Dictamnus Fraxinella!
• Cerasus avium.
• vulgaris!
• *Rosa, var. cult.!
• *Daucus Carota!
• Heracleum, sp.
• Epilobium hirsutum!
• Lathyrus latifolius.
• *Trifolium repens!
• hybridum.
• Melilotus, sp.
• Medicago, sp.
• Lonicera Periclymenum.
• Carduus heterophyllus.
• tataricus.
• Scrophularia aquatica.
• Symphytum officinale.
• Anchusa ochroleuca.
• paniculata.
• *Primula sinensis!
• Salix babylonica.
• Hyacinthus, sp.
• Tulipa, sp.

Some of the above are probably cases of mere virescence rather than of phyllody. For further illustrations, references to authorities, &c., see under Chloranthy, Virescence, Prolification, &c.

Phyllody of the ovules.—Pending the settlement of the existing differences of opinion with reference to the morphological nature of the ovule and its component parts, much interest attaches to the malformations to which they are occasionally subject. Considered purely in a teratological point of view, it seems clear that the ovular coats are usually, if not always, of foliar nature, while the central nucleus is an axial organ; but if this be so there still remains the question whether the leafy coats of the ovule are processes of the carpel itself, or distinct independent formations, like the scales of a leaf-bud; as to this latter point, the evidence is at present very conflicting. Prof. Al. Braun, who has devoted much attention to the subject, describes and figures ovules of Nigella and Adonis, wherein the outer coat of the ovule was converted into a leafy, lobed mass, like the ordinary leaves, and these he considers to be a portion, not of the carpel, but of the ovular bud; he, however, hesitates to pronounce an opinion on the nature of the pedicel of the ovule. In Primulaceæ, wherein ovular changes are very common, the leafy coat of the ovule would seem, from the nature of the placenta, to be independent of the carpel. Morren, who studied the changes in the ovules of Primula sinensis, applied the term lepyrophylly (λεπυρον, a scale) to the foliaceous condition of the testa in this plant. Unger describes a series of malformations in Primula sinensis, consisting chiefly of reversions of the part of the flower to leaves. The carpels were entirely absent in this case, and the place of the free central placenta was occupied by a circle of leaves, sometimes bearing imperfect ovules on their edges. An instance of a similar kind has been described by A. de Candolle.

In these flowers the placenta seemed to be composed of several funiculi soldered together, and bearing imperfect ovules. In other cases no traces of ovules are visible, but the funiculi are in a foliaceous condition. Moquin also alludes to a case of the same nature in Cortusa Mathioli, in which the funiculi bore little rounded leaves. Brongniart has described some malformations of Primula sinensis in which the ovules were transformed wholly or partially into small leaves with three to five lobes. Dr. Marchand mentions similar changes in Anagallis arvensis and Lonicera Periclymenum.

Cramer figures ovules of Primula sinensis in the form of stalked leaves, often becoming infolded at the margins, and giving origin to a small nucleus on their inner surface.

M. Tassi records an instance in Symphytum officinale wherein the ovules were replaced by two small linear leaves arising entirely from the axis, and not from the carpels.

In most of the foregoing illustrations the foliar portion of the ovule must have been independent of the carpel; this independence is less manifest, though probably as real in the cases now to be mentioned. In Sinapis and in Brassica oleracea foliaceous ovules may occasionally be seen, attached to the placenta by long stalks. No trace of the nucleus is visible in these specimens.

Griffith, in alluding to a similar case in Sinapis, describes the ovules as foliaceous, and having their backs turned away from the axis, the raphe being next to the axis and representing the midrib the funicle corresponding to the petiole. The outer tegument of the ovule, according to Griffith, is a leaf united along its margins, but always more or less open at its apex. No inversion can, therefore, really take place in anatropous ovules, but the blade of the leaf is bent back on the funicle, with which its margins also cohere.

Caspary, in an elaborate paper on phyllomorphy occurring in Trifolium repens, figures foliaceous ovules springing from the edge of an open, leafy carpel. The nucleus of the ovule, in these cases, appears to originate as a little bud from the surface of the leafy ovule (figs. 141, 142).

In a species of Triumfetta (see p. 260), of which I examined dried specimens, the ovary was open and partly foliaceous; it bore on its infolded margins ten erect leaflets, representing so many ovules; each leaflet was conduplicate, the back being turned towards the placenta.

On the other hand, there are cases in which the leafy coat of the ovule, in place of being a distinct organ, seems to originate from the margin of the carpellary leaf itself—to be, as it were, a lobule or small process of the carpel, and not an absolutely new growth. Thus, Planchon, from an examination of some monstrous flowers of Drosera intermedia, was led to the inference that the ovules are analogous to hairs on the margins of the leaves. This acute botanist was enabled to trace all the gradations between the simple cup formed by the confluence of four glanduliferous hairs and the concave leaf and the perfect ovule.

Brongniart records ovules of Delphinium elatum existing in the form of marginal lobes of the carpellary leaf itself; so that each ovule corresponds to a lobe or large tooth of this leaf, the funiculus, as well as the raphe, being formed by the median nerve of the lateral lobe. M. Clos mentions a similar instance in Aquilegia Skinneri; and another is figured in Lindley's 'Elements of Botany,' p. 88, f. 180.

Cramer, from an examination of several ovular malformations, as well as from the investigation of the mode of evolution of the ovules, is led to a similar conclusion with reference to the production of ovules from the modified lobes of the carpellary leaf. Figs. 143–145, copied from Cramer, show how the nucleus of the ovule is formed as a new growth from the surface of the lobes of the leaf in Delphinium elatum.

One of the most singular instances of ovular malformation in record is that cited by the Rev. M. J. Berkeley, in the 'Gardener's Chronicle,' September 28th, 1850, p. 612. The plant was a carnation, and its placenta bore, not only ovules, but also carpels (fig. 146), the latter originating in a perverted development of the former, so that many intermediate stages could be traced between the ordinary ovule and the ovary (fig. 147, 1, a, 2, b). Some of these carpels, thus derived from the ovules, themselves bore secondary ovules on a marginal placenta, as shown in the sections at c, d, e. Could such a change occur in the animal kingdom, there would be the unfertilised ovum converted into an ovary, and this again bearing Graafian vesicles! In Mr. Berkeley's carnation the change was not so great, seeing that the nucleus of the ovule was not developed, and sufficient evidence has been above given as to the foliar nature of the primine, while for a leaf to be folded up so as to form a carpel is an ordinary occurrence.

It is worthy of remark that in these foliaceous ovules there is never more than one coat, the secondine and other integuments do not make their appearance in these cases, and that very generally the change in question accompanies a similar foliaceous condition in the carpel, the margins of which are more or less disunited.

Prof. A. Braun remarks that up to this date no such change has been observed in the ovules of Monocotyledons.

Changes in the nucleus of the ovule.—The preceding remarks have had reference especially to the ovular coats, but it is desirable also to allude to certain points connected with the nucleus. Very frequently, when the coat of the ovule is phylloid, as before described, the nucleus is altogether wanting, though sometimes it is present as a small cellular papilla; very rarely is it to be found in its perfect state. Occasionally the nucleus is present in the guise of a small elongated branch. Wigand cites ovular buds in every stage of progress into a branch, sometimes even bearing indications of anthers. Wydler has observed a similar occurrence in ovules of Alliaria officinalis, and Schimper has described and figured specimens of Nigella damascena in which the outer coats of the ovule were but little changed, while the nucleus was replaced by a leafy shoot. On one of the leaves of this latter was found an imperfect ovule—an ovule on an ovule!

Fig. 148 shows a floret of a species of Gaillardia, in which the ovule was replaced by a leafy shoot which had made its way through a chink in the ovary. In this specimen, however, there was no evidence to show whether the shoot in question was a perverted development of the nucleus, or whether it was wholly independent of the ovule.

From this occasional elongation of the nucleus, as well as from the foliar nature of the ovular coats, Prof. Alex. Braun arrives at the conclusion that the ovule is to be looked on as a bud, the ovular coatings, so often variable in number, representing the scales of the bud, the nucleus corresponding to the end of the axis or growing point. Griffith had previously expressed the same opinion from his observations on malformed ovules of Sinapis and Lonicera, while Caspary's conclusions from the foliaceous ovules of Trifolum repens are somewhat similar. The latter observer considers that the funiculus, with the integuments, is the equivalent of a leaflet, the petiolule or midrib of which answers to the funiculus, and its hollow expansion to the integument. The nucleus itself is considered to be a new formation analogous to a shoot.

M. van Tieghem's conclusion from the examination, of flowers of Tropæolum majus, in which the ovules were replaced by perfect peltate leaves, is that the ovules are foliar productions springing, not directly from a prolonged floral axis, as in Primulaceæ, but from branches of the axis arising from the axils of the carpellary leaves.

Phyllody of the ovules has been met with most often in the following species:

• *Aquilegia vulgaris!
• Skinneri.
• Delphinium crassicaule.
• elatum.
• dictyocarpum.
• Ajacis.
• Nigella damascena.
• Adonis autumnalis.
• Cheiranthus Cheiri!
• Nasturtium, sp.
• Sisymbrium officinale!
• Brassica napus!
• *olcracea!
• *Alliaria officinalis!
• Sinapis arvensis!
• Turritis, sp.
• Thlaspi arvense.
• Erucastrum Pollichii.
• Stellaria media.
• *Reseda lutea.
• Drosera intermedia.
• Agrostemma Githago.
• Stellaria media.
• Triumfetta, sp.!
• Tropæolum majus!
• Dictamnus albus.
• Fraxinella!
• Caram carui
• Pastinaca sativa.
• Torilis anthriscus.
• Thysselinum palustre.
• Epilobium palustre.
• Rosa, sp.
• Fragaria alpina.
• *Trifolium repens!
• Medicago maculata.
• Desmodium canadense.
• Melilotus macrorhiza.
• Lonicera, sp.
• Gaillardia!
• Crepis, sp.
• Phyteuma odorata.
• Symphytum Zeyheri.
• *officinale.
• Stachys sylvatica.
• Anagallia arvensis.
• phœnicea.
• Lysimachia ephemerum.
• *Primula sinensis!
• Auricula.
• prænitens.
• Gilia glomeruliflora.
• Rumex arifolius.
• scutatus.
• Salix capræa.

The following list of publications relating to ovular malformations is copied from A. Braun, 'Ueber Polyembryonie und Keimung von Cælobogyne' (Appendix), to which are also added some others not alluded to by that author and not specially referred to in the preceding pages:

Jaeger, 'Missbilld. d. Gewächse,' p. 78, 79, f. 47. Rœper, 'Enum. Euphorb.,' 1824. p. 45, Delphinium.—Schimper, 'Flora,' 1829, pp. 437–8, et 'Mag. fur Pharmacie de Geiger,' 1829–30, pl. iv-vi, text wanting, Primula, Reseda, Cheiranthus.—Engelmann, 'De Antholysi,' 1832.—Valentin, 'Act. Acad. Nat. Cur.,' 1839, p. 225, Lysimachia.—Unger, 'Act. Acad. Nat. Cur.,' xxii, 11, 1850, p. 543, t. 5 B, Primula.—'Flora (B. Z.)', 1842, p. 369, t. ii, Trifolium.—Brongniart, 'Ann. Sc. Nat.,' 1834, ii, p. 308; also 'Archives Mus. d'Hist. Nat.,' 1844, t. iv, p. 43, pl. iv, v, Primula.—Reissek, 'Linnæa,' xvii, 1843, Alliaria.—Wydler, 'Denkshrift. d. Regensb. Bot. Gesell.,' 1855, iv, s. 77, t. vii, Alliaria.—Wigand. 'Grundlegung der Pflanzen Teratol.,' 1850, p. 39, Turritis.—Wigand, 'Bot. Untersuchungen,' 1853, p. 23, Rosa, Turritis, Crepis.—Germain de St. Pierre, 'L'lnstitut,' 1853, n. 1051, p. 351.—Rossmann, "Entwicklung der Eiknospen aus dem Fruchtblatte," &c., 'Flora,' 1855, pp. 647 and 705.—Dareste, 'Ann. Sc. Nat.,' 1842, p. 220, Delphinium.—Fresenius, 'Mus. Senkenb.,' ii, p. 39, t. iv, f. 9, Primula.—Schultz, 'Flora o. d. Bot. Zeit.,' 1834, xvii, p. 121, Nasturtium.—Seringe and Heyland, 'Bull. Bot.,' 1–7, Diplotaxis.—Clos, 'Mem. Acad. Toulouse,' vi, 1862, Delphinium.—Morren, C., 'Bull. Acad. Belg.,' xix, part ii, p. 519, Primula.—Caspary, 'Schrift. d. Physik. Œk. Gesell. zu Königsberg,' band ii, p. 51, tabs. ii, iii. Fleischer, 'Ueber Missbildungen Verschiedener Cultur Pflanzen.,' &c., Esslingen, 1862. Cramer, 'Bildungsabweich,' p. 68, &c. &c., Trifolium.—Moquin-Tandon, 'El. Terat. Veg.,' p. 206, Cortusa.—Guillard, 'Bull. Soc. Bot. Fr.,' 1857, vol. iv, p. 761, Stellaria.—Moelkenboer, 'Tijdschrift v. Natuurl. Geschied.,' 1843, p. 355, t. vi, vii, Primula.—Van Tieghem, 'Bull. Soc. Bot. Fr.,' 1865, p, 411, Tropæolum.

Phyllody in accessory organs.—In addition to the ordinary organs of the plant, what are termed the accessory organs, such as hairs, spines, &c., sometimes become foliaceous. It is not to be wondered at that spines, when they represent the framework of a leaf, become sometimes clothed with cellular tissue, and thus become indeed true leaves. This happens occasionally in Berberis; a similar thing occurs in the stipules of some Leguminosæ; the scales of some begonias; the tendrils of Bignonia, Cobæa, &c.

The presence of two small green laminæ on the outer side of the two posterior stamens in Antirrhinum majus has also been met with. The adventitious organs appeared as if they were developments from the thalamus—a kind of foliaceous disc, in fact.

Chloranthy.—The term phyllomorphy is applied to the individual parts of the flower which assume the form and appearance of leaves. By chloranthy it is to be understood that all, or the great majority of the organs of the flower assume these conditions. In chloranthy, as here defined, there is no unusual number of buds, as there is in prolification, but the appearance of the flower-bud is so changed as to make it resemble more closely a leaf-bud than a flower-bud. There is not necessarily any increase in the number, or any alteration in the position of the buds, but the form and appearance of the latter differ from what is usual. Chloranthy, then, is a more complete form of frondescence. Owing to the vagueness with which the word has been applied by various authors, it becomes very difficult to ascertain whether the recorded instances of chloranthy were really illustrations of what is here meant by that term, or whether they were cases of mere virescence (green colour, without other perceptible change), or of prolification (formation of adventitious buds). It is, therefore, quite possible that some of the instances to be now mentioned were not strictly cases of chloranthy.

Seringe has described a malformation in Diplotaxis tenuifolia in which all the floral organs were replaced by sixteen distinct leaflets which had preserved their proper relative position. The Cruciferæ, of which family the last-named plant is a member, are particularly liable to this malformation, as also are the Rosaceæ, as will be seen from the following illustrations. Roses indeed often exhibit alterations of this kind as the commencement of prolification. There is also in cultivation a rose called the green rose, "Rose bengale à fleurs vertes," in which all the parts of the flower are represented by leaves. One of the most remarkable features in this plant is, that the carpels have often two ovules on their margins. Now, Payer, in his "Organogénie," has shown that at a certain period of the development of the ordinary rose flower the ovary contains two collateral ovules, of which one becomes in process of time suppressed. Geum coccineum has been found by Wigand with its flowers in this condition.

Lindley figures a very interesting illustration in Potentilla nepalensis, in which some of the flowers have their component parts leafy, in others the receptacle lengthens, till in extreme cases the whole of the floral apparatus is represented by a branch bearing a rosette of leaves.

A particular variety of the Alpine strawberry is also described as occasionally subject to this transformation. In these flowers the calyx remains normal, while all the other parts of the flower, even to the coating of the ovule, assume a leaf-like condition.

Among Leguminosæ a partial leafy condition (frondescence), or a more complete degree of the same change, (chloranthy) is not infrequent, particularly in Trifolium repens. In this species the changes are so common, so various and important, that they may be alluded to in some little detail. M. Germain de Saint Pierre, in commenting on the frequency with which the flowers of this plant are more or less frondescent, remarks that although all the flowers on one plant may be affected, they are all changed in the same manner, but on different specimens different degrees of transformation are found. In all the corolla and stamens are comparatively little removed from the ordinary form, the calyx and pistil, however, have a particular tendency to assume a foliar condition. The author just cited arranges the malformations of this plant under three heads, as follows:

1. Calyx-teeth larger than usual, sometimes dentate at the margin; petals more or less regular and disposed to run away from the papilionaceous form; filaments free; anthers normal; carpel transformed into a true leaf with a long stalk provided at the base, with two stipules, terminal leaflet, solitary, green, with no trace of ovules. Sometimes a second carpellary leaf, similar to the first, is formed; in other cases the central axis of the flower is occasionally prolonged into a head of young flowers—median prolification. In some few instances the calyx is not at all altered, but the carpellary leaf is trifoliolate, or even quinquefoliolate, the corolla being then absent. The heads of flowers in this first form have the aspect of little tufts of leaves.

2. Each of the teeth of the calyx is represented by a long stalk, terminated by a single articulated leaflet, the bi-labiate form of the calyx is still recognisable; the two upper petals are united, the three lower separate; the tube of the calyx is not deformed and seems to be formed of the petioles of the sepals united by their stipules. In this second class of cases the corolla is papilionaceous, the filaments free, the carpellary leaf on a long stalk provided with stipules, its blade more or less like the usual carpel, with its margins disunited or more commonly united with the ovules in the interior, sometimes represented by a foliaceous, dentate primine only. In one case the carpel was closed above, gaping below, where it gave origin to several leaflets, the lower ones oval, dentate, like ordinary leaflets, the upper ones merely lanceolate, leafy lobes, representing the primine reduced to a foliaceous condition. Inflorescence—a head with leafy flowers on long stalks, which are longer at the circumference than in the centre.

3. Calyx-teeth lance-shaped, acuminate; corolla more or less regular, arrested in its development and scarcely exceeding the tube of the calyx within which it is crumpled up; stamens but little changed; carpellary leaf on a short stalk, not exceeding the calyx tube, but the ovarian portion very long, and provided with abortive ovules.

These three groups will be found to include most of the forms under which frondescence of the clover blossoms occurs, but there are, of course, intermediate forms not readily to be grouped under either of the above heads. Such are the cases brought under the notice of the British Association at Birmingham in 1849 by Mr. R. Austen, in some of which the petals and stamens even were represented by leaves.

Although, on the whole, chloranthy is most frequent in the families already alluded to, yet it is by no means confined to them, as the examples now to be given amply show. Specimens of Nymphæa Lotus have been seen in which all the parts of the flower, even to the stigmas, were leafy, while the ovules were entirely wanting.

Planchon figures and describes a flower of Drosera intermedia that had passed into a chloranthic condition, excepting the calyx, which was unchanged; the petals, like the valves of the ovary, were provided with stipules, and were circinate in vernation.

M. A. Viaud-Grand-Marais records an interesting example of chloranthy, in which the sepals, petals, pistils, and ovules of Anagallis arvensis were all foliaceous. Similar changes have not unfrequently been met with in Dictamnus Fraxinella.

M. Germain de Saint Pierre has also recorded the following deviations in the flowers of Rumex arifolius and R. scutatus; in these specimens the calyx was normal, the petals large, foliaceous, shaped like the stem-leaves, the stamens were absent, the three carpels fused into a triangular leafy pod, as long again as the perianth, the stigmas normal or wanting, the ovule represented by a thick funicle, terminated by a foliaceous appendage analogous to the primine.

In grasses it frequently happens that the flowers are replaced by leaf-buds; this condition is alluded to elsewhere under the head of viviparous grasses, but in this place may be mentioned a less degree of change, and which seems to have been a genuine case of chloranthy in Glyceria fluitans, the spikelet of which, as observed by Wigand, consisted below of the ordinary unchanged glumes, but the remaining paleæ as well as the lodicles and stamens were represented by ligulate leaves. The plant, it is stated, was affected by a parasitic fungus. On the other hand, General Munro, in his valuable monograph of the Bambusaceæ, refers to an illustration in which "the lowest glumes generally, and the lowest paleæ occasionally, had the appearance of miniature leaves, with vaginæ, ligules and cilia, enveloping, however, perfect fertile spiculæ; as progress is made towards the top of the spike, the ligule first, then the cilia, and finally, the leaf-like extension disappears, and the uppermost glumes assume the ordinary shape and form of those organs."

General remarks on chloranthy and frondescence.—Moquin remarks with justice that the position of the flowers on the axis is of importance with reference to the existence of chloranthy. Terminal flowers are more subject to it than lateral ones, and if the latter, by accident, become terminal, they seem peculiarly liable to assume a foliaceous condition. Kirschleger says, that in Rubus there are two sorts of chloranthy, according as the anomaly affects the ordinary flowering branches, or the leafy shoots of the year, the summits of which, instead of developing in the customary manner, terminate each in one vast and long inflorescence, very loose and indeterminate, and with axillary flowers.

On the whole, taking in consideration cases of partial frondescence, as well as those in which most of the parts of the flower are affected, phyllody would seem to be most common in the petals and carpels, least so in the case of the stamens and sepals. It is more common among polysepalous and polypetalous plants than in those in which the sepals or petals are united together.

The causes assigned for these phenomena are chiefly those of a nature to debilitate or injure the plant; thus it has been frequently observed to follow the puncture of an insect. M. Guillard gives an instance in Stellaria media where the condition appeared to be due to the attacks of an insect Thrips fasciata. Still more commonly it arises from the attacks of parasitic fungi, e.g. Uredo candida, in Crucifers, &c.

In other cases it has been observed when the plants have been growing in very damp places, or in very wet seasons, or in the shade, or where the plant has been much trampled on. This happens frequently with Trifolium repens. The frequency with which the change is encountered in this particular species is very remarkable; it is difficult to see why one species should be so much more subject to the kind of change than another of nearly identical conformation.

It might at first be supposed that the same causes that bring about the complete substitution of leaf-buds for flower-buds (see Heterotaxy) would operate also in the partial substitution of leaves for other parts of the flower, but it will be seen that the inducing cause, whether similar or not in the two cases respectively, acts at different times; in the one case, it is not brought into play until the rudiments of the flower are already formed, whereas in the other the influence is exerted prior to the formation of the flower. So that while the formation of leaf-buds in place of flower-buds may be and generally is due to an excess of nutrition, inducing over activity of the vegetative organs, the production of phyllomorphic or chloranthic flowers may be owing rather to a perversion of development arising from injury or from some debilitating agency. The discrepancies in the assigned causes for the conditions above mentioned may, therefore, in great measure, be attributed to the different periods at which the causes in question operate.

The following list may serve as a guide to the plants most frequently the subjects of chloranthy, but reference should also be made to preceding and subsequent sections, and to that relating to prolification of the inflorescence.

• Aquilegia vulgaris.
• Chelidonium majus.
• Corydalis aurea.
• Nymphæa Lotus!
• *Brassica oleracea!
• Bunias.
• Hesperis matronalis.
• *Sinapis arvensis!
• Sisymbrium officinale.
• Erucastrum canariense.
• Diplotaxis tenuifolia.
• Lychnis dioica!
• Cerastium glomeratum!
• triviale.
• Stellaria media.
• Poterium polygamum.
• Torilis anthriscus.
• Seseli, sp.
• Selinum caruifolium.
• Epilobium hirsutum!
• Begonia fuchsioides.
• Gomphia, sp.
• Scabiosa Columbaria.
• Dipsacus fullonum.
• Matricaria Parthenium.
• Calendula officinalis.
• Campanula pyramidalis.
• Reseda odorata!
• Vitis vinifera.
• Dictamnus Fraxinella!
• Triumfetta, sp.!
• *Tropæolum majus!
• Rhamnus Frangula.
• *Trifolium repens!
• Lupinus, sp.
• Rosa diversifolia!
• Potentilla nepalensis.
• argentea.
• Fragaria vesca!
• Geum rivale.
• Rubus fruticosus.
• cæsius.
• Saxifraga foliosa.
• Verbascum phlomoides.
• Scrophularia nodosa.
• aquatica!
• *Primula sinensis!
• Lysimachia Ephemerum.
• Anagallis arvensis.
• Webbiana.
• Nicotiana rustica.
• Anchusa ochroleuca.
• Myosotis cæspitosa.
• Stachys sylvatica.
• Gilia capitata.
• Euphorbia segetalis.
• Rumex arifolius.
• scutatus.
• Juncus lampocarpus.
• uliginosus.

In addition to the publications before cited the following may be named as containing valuable information on the subject of this chapter.

Jæger, 'Missbild. Gewächs.,' 1814, p. 83, Trifolium repens. For other accounts of similar malformations in the same plant, see Schmitz, 'Linnæa,' xv, p. 268. Unger, 'Flora' (B. Z.) xxv, p. 369. Caspary, 'Schrift. der. Physik. ökon. Gesellsch. zu Königsberg,' 2, 1861, p. 51, tabs. ii, iii. Fleischer, 'Missbilld. verschied. Cult. Pflanz.,' 1862, p. 55, &c., t. v, vii, &c. For Primula see Brongniart, 'Ann. Sc. Nat.,' ser. 2, t. i, p. 308. A. P. and Alph. De Candolle in 'Neue Denkschrift.' Morren, C., 'Bull. Acad. Roy. Belg.,' xix, part 2, p. 539. Molkenboer, 'Tijdschr. voor Natuurl. Geschied.,' 1843, p. 355, tabs. vi, vii. Marchand, 'Adansonia,' iv, p. 167 and p. 159. Anagallis, p. 171, Lonicera, p. 83, Juncus. For other plants see Fresenius, 'Mus. Senk.,' 2, p. 35, &c. Norman, 'Ann. Sc. Nat.,' ser. 4, 1858, vol. ix, p. 220. Christ, 'Flora' (B. Z.) 1867, p. 376, tabs. v, vi, Stachys. Cramer, 'Bildungsabweich.,' p. 26, &c. Baillon, 'Adansonia,' ii, p. 300. Moquin-Tandon, 'El. Ter. Veg.,' p. 230. Schauer's translation, p. 220. Hallier, 'Phytopathologie,' p. 160.

Chapter II. Metamorphy of the Floral Organs.

One of the main arguments adduced by Goethe and others in support of the now generally received doctrine of the essential morphological identity of the various whorls of the flower is derived from the frequent appearance of one organ in the guise of another. The several parts of the flower become, as it is said, metamorphosed; sometimes the change is complete, while at other times there may be every conceivable intermediate condition between one form and another. The sense in which the terms metamorphosis, substitution, transformation, and the like, are herein used has already been explained. For the convenience of arrangement, metamorphosis of the parts of the flower may be divided into several subdivisions, according to the particular organ affected, and according to the special kind or degree of change manifested, the main subdivisions being here classed as Sepalody, Petalody, Staminody, and Pistillody.

Sepalody of the petals.—This change, spoken of by most authors as retrograde metamorphosis of the petals into sepals, or as a substitution of sepals for petals, is obviously a condition that is in most cases hardly distinguishable from virescence of the corolla, or from multiplication of the sepals. Nor is this of much consequence unless there are some special structural features which render the discrimination a matter of importance, in which case the difficulty is generally easily surmounted. The flower of the Saint-Valèry Apple may perhaps be cited under this head. In the flower in question there are neither stamens nor petals, unless the second or inner of sepals be considered as sepaloid petals (fig. 152).

M. Alph. de Candolle describes an instance in Primula Auricula in which the corolla had assumed the appearance of the calyx, but neither calyx nor corolla in this case possessed perfect stomata.

This malformation is much less common than the converse one of calycanthemy. Many of the recorded instances of so-called metamorphosis of the parts of the flower to sepals have occurred in monocotyledonous plants, or others in which the calyx and corolla are of the same colour, and constitute what is frequently termed the perianth; and as this is usually brightly coloured (not green) it is more convenient to group the metamorphoses in question under the general term Petalody, which thus includes all those cases in which the organs of the flower appear in the form of coloured petal-like organs, whether they be true petals or segments of a coloured perianth. As the morphological difference between the organs is one of position merely, there is little objection to be raised to this course, the less so as the term petalody merely conveys an idea of resemblance and not of absolute identity.

Petaloid coloration of the ordinary leaves, or of the bracts, is mentioned under the chapter relating to colour.

Petalody of the calyx—Calycanthemy.—As with the bracts, so the calyx in certain instances is naturally coloured, as in Delphinium, Tropæolum, and others. In Mussænda, Calycophyllum, Usteria, &c., one or more of the calyx lobes become enlarged normally. Considered teratologically, petaloid coloration of the sepals is either general or partial; in the latter case the nerves retain their green colour longest. There is in cultivation a variety of the primrose called Primula calycanthema, in which the upper part of the calyx becomes coloured, so that the flower seems to have two corollas placed one within the other; a similar thing happens in Mimulus, in which plant, as the calyx is permanent while the corolla is deciduous, the coloured calyx is a great advantage in a horticultural point of view. Morren says that in order to produce the fine colour of the calyx of Primula officinalis (var. smaragdina) the Belgian gardeners cut away the corolla in a very early stage, and that in consequence the colouring matter proper to the corolla is developed in the tube of the calyx, the edges of the limb remaining green, the middle of the limb being purple (Primula tricolor).

Under this head may be mentioned the occurrence of tubular sepals in place of the ordinary flat ones in Helleborus olympicus; only two of the sepals were thus affected in a specimen recently observed—a third exhibited an intermediate condition.

The normal coloration of the calyx occurs most frequently in polysepalous calyces; teratological coloration, on the other hand, occurs especially in gamosepalous flowers. This assertion is borne out by the frequency of the change in the plants already mentioned, and also in the following:—Campanula persicifolia, Anagallis arvensis, Gloxinia, Syringa persica, Calceolaria, &c. &c. In the last-named plant one or more of the lobes of the calyx may frequently be seen replaced by a slipper-like petal.

Among polysepalous plants petaloid sepals have been observed in Ranunculus auricomus, Rubus cæsius, &c. Fleischer also describes a case of this kind in Carum carui.

It will be seen from the above that in the majority of cases there is no real metamorphosis or substitution of petal for calyx, but simply an alteration in colour; nevertheless, a change in form may accompany a change of colour: this happens especially if there has been any displacement of organs. Thus, if, in an orchidaceous plant, a sepal be displaced from any cause, or a petal be twisted out of its natural position to occupy the place of an absent sepal, that petal will be sepal-like in form, and vice versâ.

Petalody of the stamens.—A petaloid condition of the stamens is one of the commonest of all malformations. A large number of so-called double flowers (flores pleni) owe their peculiar appearance to this circumstance.

It is necessary to distinguish carefully this petaloid development of the stamens from the corresponding condition of the pistils, and from that kind of doubling which is a result of multiplication of the corolla, as in Datura, Campanula, Primula, &c. (flores duplices, triplices, &c.), or from that produced by true median prolification (flores geminati, &c.).

In cases of true petaloid development of the stamens there are usually numerous intermediate forms between that of the true petals and that of the perfect stamens; indeed, in Nymphæa, Canna, and in some other plants, such a transition occurs normally. Petalody of the stamens may occur either without material change in the flower or it may exist in combination or in conjunction with an increased development of parts (Multiplication), or with a similar change in the carpels, and it is either partial or complete.

Among the flowers in which petaloid development of the stamens happens most frequently may be mentioned those in which the calyx is normally coloured, as in Nigella damascena, Aguilegia, and Delphinium.

M. Alph. de Candolle, in the 'Neue Denkschriften,' 1841, described and figured a singular form of Viola odorata, known under the name of "Bruneau," in Switzerland, in which the stamens are absent, and their place supplied by a second row of petals, within which is a third series of petals, representing, says M. de Candolle, the inner row of stamens that theory suggests should exist in the natural condition. Moreover, the carpels in this variety are five in number instead of three. In Erica Tetralix the corolla may not unfrequently be found divided to the base into its constituent petals, and the place of the stamens occupied by a series of petal-like structures entirely destitute of anther.

In monocotyledonous flowers, especially those with a coloured perianth, the substitution of segments of the perianth for stamens occurs not unfrequently. M. Seringe has observed this in the stamens of Lilium Martagon, and there is in cultivation a variety of the white lily, Lilium candidum, sometimes called the double white lily, in which the segments of the perianth, in place of being arranged in two rows, are greatly increased in number, and disposed in a spiral manner. In these flowers, not only are the stamens and pistils thus modified, but also the upper leaves of the stem. In so-called double tulips there is likewise a replacement of stamens by coloured segments of the perianth, but this happens generally in connection with an increase in the number of organs. Moquin-Tandon remarks having seen in a garden in the environs of Montpelier a tulip, the stamens of which showed all possible stages of transition between the form proper to them and that of the perianth. The pistil in this case was transformed into several small leaves. Similar appearances have been observed in Iris, Hyacinths, Narcissus, Colchicum, and Crocus. M. Fournier describes a flower of Narcissus Tazetta from within the normal perianth of which sprang a second one, equally provided with a cup and occupying the space usually filled by the stamens. Flowers of Narcissus poeticus may also be met with in which the stamens are replaced by six distinct segments exactly resembling those of the perianth in miniature.

From an examination of these flowers it becomes evident that petalification is brought about in different flowers in different ways; sometimes it is the filament which becomes petaloid, sometimes the anther-lobes, while at other times it is the connective which assumes the appearance of petals. For instance, in Solanum tuberosum, S. Dulcamara, in Anagallis, in Fuchsia, and some other plants, the anther-lobes themselves become petaloid, while the filament remains unchanged.

In gardens two distinct varieties of Columbine are cultivated, the one in which the filaments are dilated into the form of flat petals almost entirely or quite destitute of anthers, while in the other the filament is present in its usual form, but the anther is developed in the shape of a tubular hood or spur.

De Candolle observes that in the Ranunculaceæ the species of Clematis become double by the expansion of the filament, those of Ranunculus by the dilatation of the anther, and those of Helleborus by the petal-like development of both filament and anther. In some cases even on the same plant all three modifications may be seen, as in Camellias, some of which may be found with petaloid filaments with anthers on the top, others with the filaments unchanged, but supporting petaloid anthers, while in others it is the connective alone which is petal-like. Where the flower naturally contains a large number of stamens, as in Mallows, Roses, Magnolias, &c., petaloid expansion of the filament is most common, though it is by no means confined to such flowers, the change occurring in Allamanda cathartica, Jasminum grandiflorum, and many other flowers with few stamens. A similar change in the anther and connective takes place more frequently in flowers where the number of stamens is smaller, but there are of course numerous exceptions to this rule.

In those cases where there is more than one row of stamens, the outermost are most liable to this change: thus in Saxifraga decipiens, as shown by Ch. Morren, the outer series of stamens—those opposite to the sepals—become first affected, and, at a more advanced stage, the inner row also; and this is the case in most flowers that have their stamens in two rows. Occasionally it happens that an outer series of stamens is abortive, or wholly suppressed, while the inner row becomes petalodic; this was the case in some flowers of Lilium auratum lately exhibited by Messrs. Veitch.

Those flowers in which only a portion of the stamens undergo this change are called semi-double, while in other cases that will be hereafter mentioned, not only are the stamens thus rendered petaloid, but their number is also augmented, as in most double roses, pinks, anemones, poppies, &c.

In some double flowers, in which the stamens assume more or less completely the appearance of petals, a singular appearance is afforded by the presence of four wing-like processes emanating from the central filaments, two on each side, so that the arrangement may be compared to two sheets of paper folded in the centre and adherent in that situation, though perfectly separate elsewhere, except sometimes at the top, where they form a sort of hood. This change results from an imperfect petalody of the anther; the two wings on each side of the central vascular cord represent the front and back walls of an anther lobe, or rather of that portion of the anther which, under ordinary circumstances, produces pollen. In the malformed flowers no pollen is formed, at least in the more complete states of the malformation, but the walls of the anther lobe become preternaturally enlarged, and petaloid in texture and appearance. This change occurs in some semi-double rhododendrons and azaleas, in crocuses, and in a species of violet found at Mentone by Mr. J. T. Moggridge.

There are numerous intermediate forms wherein the wing-like processes may be traced all the way along the filament till they ultimately lose themselves in the anther-lobes, with which they become continuous. In some cases, as in Crocus and Rhododendron, this is shown even more clearly by the existence of two perfect pollen-sacs or quarter-anthers, the remaining portions being petaloid and continuous with the dilated filament. Not unfrequently these semi-petaloid stamens adhere to the fronts of the petals, and then it appears, at a first glance, as if three organs were stuck together, one in front of another, while in reality there are but two. (See antè, p. 35, fig. 12.)

The change in the anther, above alluded to, must not be mistaken for that far more common one in which only a small portion of the anther becomes petaloid, forming a sort of lateral wing or appendage to the polliniferous portion, as happens normally in Pterandra, and is common in some double fuchsias. In this latter instance there is but a single wing, and the nature of the case is obvious.

Double flowers of Orchidaceæ generally arise from petalification of the filaments, with or without other coincident changes. What makes double flowers in this order the more interesting is the development, in a petaloid condition, of some or all of those stamens which under ordinary circumstances are wholly suppressed, so that the morphological structure of the flower, at first a matter of theory, becomes actually realised. Fig. 156 is a diagram showing the presence of two additional labella within the ordinary one in a species of Catasetum, and representing two petaloid stamens, thus evidently completing the outer staminal whorl, of which there is usually but a single representative (see Peloria, Multiplication, Prolification). In some of these double orchids it is, however, necessary not to confound a petaloid condition of the existing column with the development of usually suppressed stamens in a petaloid form. Thus, in Lycaste Skinneri the column is frequently provided with two petal-like wings, which might readily be supposed to be two stamens of the inner whorl adherent to the column; a little attention, however, to the relative position of these adventitious wings is generally sufficient to enable the observer to ascertain the true nature of the appearance.

Some forms of duplicate or hose in hose corollas are apparently due, not so much to the formation of a second corolla within the first, as to the presence of an inner series of petal-like stamens, which, by their cohesion, form a second pseudo-corolla within the first. The staminal nature of this pseudo-corolla is inferred from the occasional presence of anthers on it. In Datura fastuosa, as well as in Gloxinia, a pseudo-corolla of this kind sometimes occurs with the addition of a series of petaloid stamens attached to its outer surface.

When the petalody specially affects the anther-lobes, as in Arbutus, Petunia, Fuchsia, &c., the venation of the petal-like portion is very frequently laminar, thus tending to show that the anther is in such cases really a modification of the blade of the leaf; but as, on the other hand, we often find petal-like filaments bearing pollen-sacs on their sides, it is clear that we must not attribute the formation of pollen to the blade of the leaf only, but we must admit that it may be formed in the filament as well.

Petalody of the connective is of less frequent occurrence than the corresponding change in the other portions of the stamen. It may be seen in some forms of double columbine, in which the connective forms a tubular petal or nectary, and in double petunias and fuchsias. When it occurs, the true anther-lobes are usually atrophied, and little or no pollen is formed.

An occurrence of this nature in Tacsonia pinnatistipula, in conjunction with the partial detachment of the stamens from the gynophore, led Karsten to establish a genus which he called Poggendorffia.

From the subjoined list of genera in which petalody of the stamens, in some form or other, has been observed, it will be seen that it happens more often in plants with numerous distinct organs (Polypetalæ, Polyandria, Polygynia, &c.) than in other plants with a smaller number of parts, and which are more or less adherent one to the other. The tendency to petalification is, moreover, greater among those plants which have their floral elements arranged in spiral series, than among those where the verticillate arrangement exists; and in any given flower, if the stamens are spirally arranged while the carpels are grouped in whorls, the former will be more liable to petalody than the latter, and vice versâ. It has been before remarked, that this condition is far more common in plants whose petals, &c., have straight veins, like those in the sheath of a leaf, than in those the venation of which is reticulate, as in the blade of the leaf. It must also be remembered that in the same genus, even in the same species, different kinds of doubling occur. Familiar illustrations of this are afforded in the case of anemones, columbines, fuchsias, and other plants.

The existence of "compound stamens" in some flowers, as pointed out by Payer, and others, and the researches of Dr. Alexander Dickson, confer additional importance on the subject of petalody, and necessitate the examination of double flowers with special reference to these compound stamens, and to the order of their development. The presence of these compound stamens affords a satisfactory explanation of the appearance in some double Malvaceæ, wherein the tufts of adventitious petals are very liable to be mistaken for buds, produced by axillary prolification in the axils of the petals, but which are in reality compound and petaloid stamens. At other times, however, true axillary prolification exists in these flowers; but then the supplemental florets have always a calyx, which is wanting in the other instances.

Petalody of the stamens has been met with most frequently in the following genera:

• *Ranunculus!
• *Anemone!
• *Papaver!
• *Clematis!
• *Hepatica!
• *Ficaria!
• Thalictrum.
• *Caltha!
• *Trollius!
• *Nigella!
• *Aquilegia!
• *Delphinium!
• *Adonis!
• *Pæonia!
• *Nelumbium!
• *Nymphæa!
• *Berberis!
• *Papaver!
• *Chelidonium!
• Sanguinaria.
• Podophyllum.
• *Mathiola!
• *Cheiranthus!
• *Iberis!
• *Cardamine!
• *Hesperis.
• *Barbarea!
• *Sinapis!
• *Brassica!
• *Helianthemum!
• *Viola!
• *Dianthus!
• *Saponaria!
• *Lychnis!
• *Silene!
• *Sagina!
• *Hibiscus!
• *Althæa!
• *Malva!
• Æsculus!
• *Geranium!
• *Pelargonium.
• *Tropæolum!
• Oxalis!
• *Impatiens!
• *Camellia!
• Thea!
• Trifolium!
• Medicago!
• *Ulex!
• Spartianthus.
• Clitoria.
• Pisum!
• Orobus!
• Genista!
• Spartium!
• Cytisus!
• Anthyllis.
• Coronilla.
• Lotus!
• *Rosa!
• *Kerria!
• *Spiræa!
• *Fragaria!
• *Potentilla!
• *Cratægus!
• Cydonia.
• *Pyrus!
• Eriobotrya!
• *Amygdalus!
• *Prunus!
• *Myrtus!
• *Punica!
• *Philadelphus!
• *Deutzia!
• *Fuchsia!
• Godetia!
• Clarkia!
• Portulaca!
• Ribes!
• Saxifraga!
• Daucus.
• Ixora.
• Serissa!
• Gardenia!
• Lonicera!
• Sambucus.
• Viburnum.
• Scabiosa.
• *Campanula!
• Platycodon!
• Calluna!
• Azalea!
• Rhododendron!
• *Arbutus!
• *Erica!
• *Anagallis!
• *Primula!
• *Jasminum!
• Syringa!
• *Vinca!
• *Nerium!
• Allamanda!
• Tabernæmontana.
• *Calystegia!
• Convolvulus!
• Ipomœa.
• *Datura!
• *Petunia!
• Solanum!
• Orobanche.
• Gentiana.
• Mimulus.
• *Antirrhinum!
• Gratiola!
• *Digitalis!
• *Linaria!
• Veronica!
• Calceolaria!
• Achimenes.
• Gloxinia!
• Clerodendron!
• Bignonia.
• Cyclamen!
• Mirabilis.
• Laurus!
• Gladiolus!
• Crocus!
• Iris!
• *Galanthus!
• Leucojum!
• Sternbergia!
• Hippeastrum.
• *Narcissus!
• *Orchis!
• Catasetum!
• Hydrocharis.
• Asphodelus.
• *Tulipa!
• Scilla.
• *Convallaria!
• Fritillaria!
• *Lilium!
• *Hyacinthus!
• *Polianthes!
• *Hemerocallis!
• *Colchicum!
• *Sagittaria!
• *Tradescantia!
• Commelyna!
• Tofieldia.

Petalody of the pistils.—Taken by itself, this is much less common than the corresponding change in the stamens. It generally affects the style and stigma only, as happens normally in Petalostylis, Iris, &c., but this is by no means always necessarily the case. In some of the cultivated varieties of Anemone and Ranunculus all the parts of the flower remain in their normal state, except the pistils, which latter assume a petaloid appearance.

Many of the double flowers owe their peculiar appearance to the combination of the following appearances—a petal-like form of the stamens, increase in the number of these organs and similar changes affecting the pistils, and is applied to several distinct conditions. If in any given flower all the stamens and all the pistils become wholly petaloid, no pollen is formed, and of course no seeds can be produced, but this very rarely happens, as usually some pollen is produced, and some ovules capable of being fertilised are developed.

In double flowers of Primula sinensis it frequently happens that the capsule is either partially leafy or partly petal-like; in either case the fruit is open at the extremity, and often destitute of the style and stigma. It is, however, doubtful if the ovules can be fertilised in these flowers.

The following list comprises the names of those genera in which this change has been most frequently observed, independently of corresponding alterations in the stamens, but it is more usual for both sets of organs to be similarly affected.

• *Ranunculus!
• *Anemone!
• Nigella.
• *Papaver!
• *Dianthus!
• Saponaria!
• Viola!
• Camellia!
• Alcea.
• Hibiscus!
• Amygdalus!
• Lonicera!
• Scabiosa.
• Æschynanthus!
• Primula!

Petalody of the ovules.—The principal changes which occur in the ovule have already been alluded to at pp. 262–272; it may here be stated, however, that the ovules are occasionally represented by small stalked petal-like structures. This happens with especial frequency among Cruciferæ.

Petalody of the accessory organs.—A petaloid condition of the disc, of the scales, or other excrescences from the axis or from the lateral portions of the flower, is of frequent occurrence, though it is but rarely that the change is of any great importance in a morphological point of view. C. Morren has given the name adenopetaly to a case wherein one of the glands at the base of the petals in Lopezia was replaced by a petal. A similar change may be seen in the double Oleander.

Staminody of the bracts.—An instance of this has been already alluded to in Abies excelsa, as observed by Prof. Dickson, and in which some of the bracts were seen assuming the form and characteristic of the stamens see ante: p. 192. Signor Licopoli met with a similar substitution of anthers for bracts in Melianthus major.

Staminody of the sepals and petals.—In the first named this is of very rare occurrence. M. Gris has recorded an instance in Philadelphus speciosus which appears to be the only case on record. The corresponding change in the case of the petals is far more common. De Candolle cites in illustration of this occurrence flowers of the common haricot, in which the alæ and carina of the corolla were thus changed. There is in cultivation a form of Saxifraga granulata wherein the petals are replaced by stamens, so that there are fifteen stamens. A similar change has been observed in Capsella bursa-pastoris.

Cramer figures and describes a stamen occupying the place of a petal in Daucus Carota. Turpin describes a similar occurrence in Monarda fistulosa, in which the lower lip terminated in an anther, but this may have been a case of adhesion. Moquin cites from Chamisso, Digitalis purpurea, and from Jussieu, Asphodelus ramosus, as having presented this change, and Wiegmann has seen anthers developed on the awns of Avena chinensis. In semi-double flowers of Ophrys aranifera and Orchis mascula, the lateral petals are occasionally partially antheroid, and others occur in which two of the outer series of stamens, which are ordinarily suppressed, are present, but in a petaloid state. Reichenbach figures an illustration of this change, and also Moggridge.

Staminody of the pistils.—The existence of this change has been denied by several authors, nevertheless, it is of sufficiently common occurrence. Alexander Braun notices the transformation of pistils into stamens in Chives (Allium Scorodoprasum), and in which three stamens appeared in the place of as many pistils, and had extrorse anthers, while the six normal anthers are introrse. In the horse-radish (Armoracia rusticana), two of the carpels are frequently converted into stamens, while two other organs absent from the normal flower make their appearance as carpels. Roeper has observed this phenomenon in Euphorbia palustris, and in Gentiana campestris. In these examples one of the carpels was apparently absent, and its place supplied by an anther. Roeper has also mentioned a balsam with a supernumerary stamen occupying exactly the position of a carpel.

Agardh has observed a similar thing in a hyacinth, one half of the fruit of which contained seeds, and the other half, anthers. B. Clarke mentions an instance in Mathiola incana in which the carpels were disunited, and antheriferous at the margin.

The passage of pistils to stamens in willows has been frequently remarked, as in Salix babylonica, silesiaca, cinerea, Caprea and nigricans. One of the most curious illustrations of this transformation in this genus is given by Henry and Macquart (Erst. Jahrb. des bot. Vereines am m. et n. Rhein., 1837). In the flowers in question the series of changes were as follows:—first, the ovary opened by a slit, and then expanded into a cup; next, anther-cells were developed on the margin of the cup, with stigmas alternating with them, the ovules at the same time disappearing; lastly, the margin became divided, and bore three perfect anthers, which in the more perfect states were raised on three filaments.

Campanula persicifolia, C. rapunculoides, and C. glomerata have been observed to present an anther surmounting the pistil. Double tulips often present this change, and a like appearance has been observed in Galanthus nivalis, and Narcissus Tazetta.

Moquin mentions the existence of this condition in a female plant of maize, some of the pistils of which were wholly or partially converted into anther-like organs. Mohl has recorded an analogous malformation in Chamærops humilis, and in which the three carpels were normally formed, and only differed from natural ovaries in this, that along the two edges of the ventral suture there was a yellow thickening, which a cross section of the ovary showed to be an anther-lobe filled with pollen.

In Tofieldia calyculata a similar substitution of a stamen for a carpel has been observed by Klotsch, and Weber gives other instances in Prunus and Pæonia. Corresponding alterations may be met with in cultivated tulips, in the cowslip and other plants. In most of the above cases the transmutation has been perfect, but in quite an equal number of cases a portion only of the carpel is thus changed, generally the style or the stigma; thus Baillon describes the stigmas of Ricinus communis as having been in one instance antheriferous. Moggridge figures a flower of Ophrys insectifera in which the rostellate process was replaced by an anther.

Mohl remarks that the change of pistils into stamens is more common in monocarpellary pistils than it is in those which are made up of several carpels. It seems clear that in this transformation the lobes of the anther and the development of pollen have no relation to the production of ovules.

Staminody of the accessory organs of the flower.—The scales that are met with in some plants, either as excrescences from the petals, or as imperfect representatives of stamens or other organs, are occasionally staminoid; thus the scales of Saponaria officinalis, of Silene, Nerium Oleander, the rays of Passiflora, the corona of Narcissus, have all been observed occasionally to bear anthers. In the case of Narcissus the loose spongy tissue of the corona seems to have the nearest analogy to the anther-lobes, while the prolonged connective is more like the ordinary segments of the perianth in texture. The species in which this change may most frequently be observed are, N. poeticus, N. incomparabilis, and N. montanus.

M. Bureau found in some flowers of Antirrhinum majus two petal-like bodies standing up in front of, or opposite to the two petals of the upper lip, and similar developments in which each of the two adventitious segments are surmounted by an anther may be met with frequently. It does not follow because these organs bear anthers that they are morphologically true stamens. They are really scales, &c., taking on themselves accidentally the characters proper to stamens.

Pistillody of the perianth.—The passage of the segments of the perianth into carpels has been observed frequently in Tulipa Gesneriana, the change in question being generally attended by a partial virescence. M. Gay is said by Moquin to have observed a flower of Crocus nudiflorus in which the segments of the perianth were cleft and fringed at the same time, so that they presented the appearance of the stigmas.

Pistillody of the sepals.—In some double flowers of the garden pea communicated by Mr. Laxton, among other peculiarities was a supernumerary 5–6-leaved calyx, some of the segments of which were of a carpellary nature, and bore imperfect ovules on their margins, while at their extremities they were drawn out into styles.

Pistillody of the stamens.—This change whereby the stamens assume more or less the appearance of pistils is more commonly met with than is the metamorphosis of the envelopes of the flower into carpels. In some cases the whole of the stamen appears to be changed, while in others it is the filament alone that is altered, the anther being deficient, or rudimentary; while, in a third class of cases, the filament is unaffected, and the anther undergoes the change in question. In those instances in which the filament appears to be the portion most implicated, it becomes dilated so as to resemble a leaf-sheath rather than a leaf-stalk, as it does usually.

One of the most curious cases of this kind is that recorded in the 'Botanical Magazine,' (tab. 5160, f. 4) as having occurred in Begonia frigida already alluded to, and in which, in the centre of a male flower, were four free ovoid ovaries alternating with as many stamens. In the normal flowers of this plant, as is well known, the male flowers have several stamens, while in the female flowers the ovary is strictly inferior, so that, in the singular flower just described, the perianth was inferior instead of being superior, as it is usually. It should be added also that the perianth in these malformed flowers was precisely like that which occurs ordinarily in the male flowers.

In some varieties of the orange, called by the French "bigarades cornues," the thalamus of the flower, which is usually short, and terminated by a glandular ring-like disc, is prolonged into a little stalk or gynophore, bearing a ring of supernumerary carpels. These carpels are isolated one from another, and are formed by the transformation of the filaments of the stamens.

The additional carpels in the case of the apple of St. Valéry, in which the petals are of a green colour, like the sepals, are by some attributed to the transformation of the stamens into carpels. These adventitious carpels frequently contain imperfect ovules and form a whorl above the normal ones. (See Pyrus dioica of Willdenow.) A similar change occasionally happens in the stamens of Magnolia fuscata, while in double tulips this phenomenon is very frequent, and among them may be found all stages of transition between stamens and pistils, and many of the parts combining the characters of both. Dunal and Campdera have described flowers of Rumex crispus, with seven pistils, occupying the place of as many stamens.

In Papaver bracteatum a considerable number of the stamens sometimes become developed into pistils, especially those which are nearest to the centre of the flower, and in these flowers the filaments are said to become the ovaries, while the anthers are curled so as to resemble stigmas. A similar change is not infrequent Papaver somniferum. Goeppert, who found numerous instances of the kind in a field near Breslau, says the peculiarity was reproduced by seed for two years in succession. Wigand ('Flora,' 1856, p. 717) has noticed among other changes the pistil of Gentiana Amarella bearing two sessile anthers. Polemonium cæruleum is another plant very subject to this change. Brongniart describes a flower of this species in which the stamens were represented by a circle of carpels united to each other so as to form a sheath around the central ovary. By artificial fertilization M. Brongniart obtained fertile seeds from the central normal ovary as well as from the surrounding metamorphosed stamens.

Cheiranthus Cheiri has long been known as one of the plants most subject to this anomaly. De Candolle even mentions it in his 'Prodromus' as a distinct variety, under the name of gynantherus. Brongniart (loc. cit.) thus refers to the Cheiranthus:—"Sometimes these six carpellary leaves are perfectly free, and in this case they spread open, presenting two rows of ovules along their inner edges, or these edges maybe soldered together, forming a kind of follicle like that of the columbine; at other times, these staminal pistils are fused into two lateral bundles of three in each bundle, or into a single cylinder which encircles the true pistil. In a third set of cases these outer carpels are only four in number, two lateral and two antero-posterior, all fused in such a manner as to form around the normal pistil a prism-shaped sheath, with four sides presenting four parietal placentæ, corresponding to the lines of junction of the staminal carpels."

In the accompanying figures (fig. 163, a-d) the nature of this change is illustrated. In some of the specimens it is easy to see that the two shorter stamens undergo the change into carpels later and less perfectly than the four longer ones, and not infrequently the outer pair are altogether absent. In most of the flowers of this variety the petals are smaller and less perfectly developed than usual.

In Lilium tigrinum, some specimens of which were gathered by Mr. J. Salter, in addition to various degrees of synanthy and other changes, some of the stamens were developed in the form of carpels, adherent by their edges so as to form an imperfect tube or sheath around the normal pistil. Fig. 164 shows one of the intermediate organs from these flowers, in which half the structure seems devoted to the formation of ovules, while the other half bears a one-celled anther. Lindley has also described a case of this kind in a species of Amaryllis.

In Saxifraga crassifolia it sometimes happens that mixed with the stamens, and originating with them, are a number of distinct and perfectly formed carpels, wholly separated from the normal carpels, in the centre of the flower. In this particular instance there is usually no intermediate condition between the stamen and the pistil. Guillemin also describes a transformation of the stamens into carpels in Euphorbia esula.

When the anther is involved it may be only partially so, or almost the whole organ may be transformed. As instances of very partial change may be cited the passage of the connective into a stigma in Thalictrum minus, or the passage of the points of the anthers into imperfect styles in some species of bamboo.

In Rosa arvensis similar transformations have been observed of a slightly more complex character than those just mentioned, and passing into more important changes, especially to the formation of pollen within ovules, formed on the edges of an open carpellodic anther (see p. 186).

Mr. Berkeley has recorded an analogous case in a gourd in which the stamens bore numerous ovules (p. 200), and Baillon describes another gourd in which certain fleshy appendages surrounding the andrœcium were provided with ovules.

Payer, in his 'Organogénie,' p. 38, mentions a stamen of Dionæa bearing not only an anther, but likewise an ovule.

Sempervivum tectorum and S. montanum, have long been noticed as being very prone to present this change. Mohl remarks that, in the transformation of the stamens to the pistil in the common houseleek, the filament of the stamen generally preserves its form, the anthers alone undergoing change. At other times, however, the transformation takes place at the same time, both in the filament and in the anther. When the stamens are numerous some of them remain in their normal state, while others, and especially the inner ones, undergo a change. Sometimes all the stamens are changed simultaneously, while at other times some of these organs may be found in which the anther is partially filled with ovules, and partially with pollen.

In the accompanying figures (fig. 165, a-h) a series of intermediate stages is shown between the ordinary stamen of Sempervivum tectorum and the ordinary carpel, from which it will be seen that the filament is little, if at all, affected, and that in those cases where there is a combination of the attributes of the stamen and of the pistil in the same organ the pollen is formed in the upper or inner surface of the leaf-organ, while the ovules arise from the opposite surface from the free edge, (b, c, d, e, f, g).

In a drawing made by the Rev. G. E. Smith of a malformed flower of Primula acaulis, and which the writer has had the opportunity of examining, the stamens are represented as detached from the corolla, and their anthers replaced by open carpels, with ovules arising, not only from their edges, but also from their surfaces, while the apex of the carpellary leaf was drawn out into a long style, terminated by a flattened spathulate stigma.

Delphinium elatum is one of the plants in which this change has been most frequently noticed.

In willows the change of pistils into staminal organs has been frequently observed. In Salix babylonica Prof. Schnizlein has described various transition stages between the carpels and the stamens, and in one instance, in addition to this change, a perfect cup-shaped perianth was present, as happens normally in Populus. Mr. Lowe also records the conversion of stamens into ovaries in Salix Andersoniana, and this by every conceivable intermediate gradation.

The following list will serve to show what plants are most subject to this anomaly. It is difficult to draw any accurate inference from this enumeration, but attention may be called to the frequency of this occurrence in certain plants, such as the Sempervivum, the wallflower, the poppy, and the heath. Why these plants should specially be subject to these changes cannot be at present stated.

By the student of animal physiology such a change as above described—equivalent to the substitution of an ovary or a uterus for a testis—would be looked on as next to impossible; the simpler and less specialised structure of plants renders such a change in them far more easy of comprehension.

• Thalictrum minus.
• Delphinium elatum.
• Magnolia fuscata.
• Bocconia cordata.
• *Papaver bracteatum!
• *somniferum!
• nudicaule.
• Dionæa muscipula!
• Barbarea vulgaris.
• *Cheiranthus Cheiri!
• Cochlearia Armoracia.
• Tropæolum majus.
• Citrus Aurantium.
• *Sempervivum tectorum!
• montanum.
• Begonia frigida!
• Cucumis, sp.
• Cucurbita Pepo.
• Pyrus Malus.
• Rosa arvensis!
• Saxifraga crassifolia!
• Myrtus, sp.
• Campanula rapunculoides.
• Polemonium cæruleum.
• Gentiana Amarella.
• *Erica Tetralix.
• Stachys germanica.
• Primula acaulis.
• Rumex crispus.
• *Salix, sp. plur.!
• Euphorbia esula.
• Glochidion.
• Asphodelus ramosus.
• Amaryllis.
• Lilium tigrinum!
• longiflorum.
• *Tulipa Gesneriana!
• var. cult. plurim.!
• Hemerocallis.
• Zea Mays.
• Bambusa, sp.

Pistillody of the ovule.—An instance of this extraordinary transformation in the carnation, as observed by the Rev. Mr. Berkeley, is given at p. 268.

Part IV. Heteromorphy.

There are certain malformations that have little in common beyond this, that they cannot readily be allocated in either of the great groups proposed by writers on teratology. There are also deformities which, unlike the majority of deviations from the ordinary structure, are absolute and not relative. While the latter are due to an exaggeration, or to an imperfection of development, or, it may be, to a partial perversion in organization, the former differ from the normal standard, not merely in degree, but absolutely. This is often the case when disease or injury affects the plant; for instance, in the case of galls arising from insect-puncture the structure is rather a new growth altogether, than dependent on mere hypertrophy of the original tissues. These absolute deformities arising from the causes just mentioned belong rather to pathology than to teratology strictly so called; but, under the head of deformities, may be mentioned sundry deviations not elsewhere alluded to.

Chapter I. Deformities.

The special meaning here attached to the term deformity is sufficiently explained in the preceding paragraph; it remains to give a few illustrations, and to refer to other headings, such as Heterotaxy, Hypertrophy, Atrophy, &c., for malformations capable of more rigid classification than those here alluded to.

Formation of tubes.—The production of ascidia or pitchers from the cohesion of the margins of one or more leaves has been already alluded to (see pp. 21, ), but there is another class of cases in which the tubular formation is due, not so much to the union of the margins of a leaf as to the disproportionate growth of some portions as contrasted with others, whence arises either a depressed cavity, as in the case of a leaf, or an expanded and excavated structure, when the stem or some portion of it is affected.

The fruit of the rose, the apple, the fig, and many others, is now generally admitted to be composed externally of the dilated end of the flower-stalk in which the true carpels become imbedded. Between such cases and that of a peltate leaf with a depressed centre, such as often occurs, to some extent, in Nelumbium, there is but little difference.

In cabbages and lettuces there not unfrequently occurs a production of leaf-like processes projecting from the primary blade at a right angle (see Enation). Sometimes these are developed in a tubular form, so as to form a series of little horn-like tubes, or shallow troughs, as in Aristolochia sipho. At other times the nerves or ribs of the leaf project beyond the blade, and bear at their extremities structures similar to those just described.

In a variety of Codiæum variegatum a similar formation may be seen to a minor extent. Even the common Scolopendrium vulgare occasionally produces small pitchers of this character, as in the varieties named perafero-corautum, Moore, and peraferum, Woll.

In carnations leaves may sometimes be seen from both surfaces, from which project long, sharp-pointed tubular spurs at irregular intervals. A very singular illustration of this is figured by Trattinick,, in which the leaves, epicalyx, sepals, and petals, were all provided with tubular spurs.

In Cephalotus follicularis rudimentary or imperfect pitchers may be frequently met with, in which the stalk of the leaf is tubular and bears at its extremity a very small rudimentary leaf-blade. It is not in all cases easy to trace the origin and true nature of the ascidium, as the venation is sometimes obscure. If there be a single well-marked midrib the probability is that the case is one of cohesion of the margins of the leaf; but if the veins are all of about equal size, and radiate from a common stalk, the pouch-like formation is probably due to dilatation and hollowing of the petiole. Again, when the result of a union of the margins of the leaf, the pitcher is generally less regular than when formed from the hollowed end of a leaf-stalk. Further information is especially needed as to the mode of development and formation of these tubular organs, so as to ascertain clearly when they are the result of a true cupping process, and when of cohesion of the margins of one or more leaves. (See Cohesion, p. 31. For bibliographical references consult also A. Braun, 'Flora v. Bot. Zeit.,' 1835, t. xviii, p. 41, Aristolochia.)

Tubular formations in the flower.—A similar formation of tubes happens in some double flowers; for instance, it is not infrequent in double flowers of Primula sinensis, in which tubular petal-like structures are attached to the inner surface of the corolla; sometimes these petaloid tubes replace the stamens, while at other times they appear to have no relation to those organs. In the particular flowers now alluded to the tubular form seems due to a dilatation, and not to a cohesion of the margins. (See Cohesion, p. 23.) These tubular petals resemble in form and colour almost precisely the normal corolla in miniature, but are not surrounded by a calyx, nor do they contain stamens, while the less perfect forms show clearly their origin from a single tube-like organ.

The formation of spurs or spur-like tubes in a quasi-regular manner has been spoken of under the head of Irregular Peloria, p. 228, but we occasionally meet with tubular processes which seem to occur in an irregular manner, and to have no reference to the symmetrical plan of the flower, and which are due probably to the same causes as those which induce hypertrophy. Such spurs have frequently been seen on the corolla of Digitalis purpurea, Antirrhinum majus, Tulipa Gesneriana, and occasionally on the sepals of Fuchsia. They are very frequent in some seasons in the corolla of certain calceolarias (C. floribunda). By Morren this production of adventitious spurs was called "Ceratomanie."

Similar processes may sometimes be seen in the capsules of Linaria vulgaris, as also in the fruits of some of the Solanums, quite without reference to the arrangement of the carpels, so that their production seems to be purely irregular.

Morren, as previously remarked, gave the name "Solenaidie" to tubular deformities affecting the stamens, a term which has not been generally adopted; the deformity in question is by no means of uncommon occurrence in some double or partially pelorised flowers, as Antirrhinum, Linaria, &c. A similar formation of conical out-growths may frequently be met with in the fruits quite irrespectively of any disjunction of the carpels.

Contortion.—An irregular twisting or bending of the stem or branches is by no means of uncommon occurrence, the inducing causes being often some restriction to growth in certain directions, or the undue or disproportionate growth in one direction, as contrasted with that in another. Hence it may arise from insect-puncture, parasitic growth, or any obstacle to the natural development. Frequently it exists in conjunction with fasciation, the ends of the branches being curved round like a shepherd's crook, from the growth on one side being so much greater than on the other. Sometimes it is a mere exaggeration of a normal condition; thus, in what are termed flexuose stems the stem twists alternately to one side or another, frequently in association with an oblique form of the leaf. This state is sometimes present to an extreme degree, as in some varieties of shrubs (Cratægus, Robinia, &c.) cultivated for their singularly tortuous branches.

Such cases as those just mentioned, however, are but slightly irregular compared to others in which the deformity exists to such an extent that the traces of the ordinary mode of growth are almost obliterated. M. Moquin-Tandon alludes to a case of this kind in a species of pine (Pinus), in which a branch ended in four unequal divisions, which were strongly curved from without inwards, then became united in pairs, these latter in their turn blending into a single mass.

In the case of some beeches growing in the forest of Verzy, near Rheims, the trunks of the trees are contorted in every direction, and, at a height of from fifteen to twenty feet, a number of branches are also given off, also much contorted, and occasionally intergrafted, so that it seems as if a heavy weight had been placed on the trees and literally flattened them. Similar malformations may occasionally be met with in the branches of the oak, and commonly in the weeping ash.

M. Fournier mentions the stems of Ruscus aculeatus rolled in a circle, others twisted spirally.

The phenomenon is not confined to woody plants, but has been met with in chicory, in Antirrhinum, and other herbaceous species.

It is very difficult in some cases to separate these instances of irregular torsion from those in which the twisting takes place in a more or less regular spiral direction. In the former case the fibres of the plant are only indirectly involved, but in the latter the fibres themselves are coiled spirally from right to left, or vice versâ (spiral torsion), while not unfrequently both conditions may be met with at the same time.

The leaves also are subject to similar deformities, of which a notable illustration has been recorded in the case of the date palm, Phœnix dactylifera, originally observed by Goethe, and figured and described by Jaeger; the leaves are folded and twisted in every direction, in consequence of the fibrous band or cord which surrounds the leaves, and which generally breaks as the leaflets increase in size, remaining from some cause or other unbroken, and thus serving to restrain the growth.

A similar irregularity of growth occurs, not unfrequently, in the case of crocus leaves, when in the course of their growth, as they push their way through the soil, their progress becomes checked either by a stone or even by frost.

Spiral torsion.—Growth in a spiral direction, and the arrangement of the various organs of the plant in a spiral manner, are among the most common of natural phenomena in plants. Fibres are coiled spirally in the minute vessels of flowering plants, and are not wholly wanting even among fungi. The leaf-organs are very generally spirally arranged; the leaf-stalks are often so twisted as to bring leaves on one plane which otherwise would occupy several. In the leaf itself we have a spiral twist taking place constantly in Alstrœmeria, in Avena, and other plants. A similar tendency is manifested in the flower-stalks, as in Cyclamen and Vallisneria, and the whole inflorescence, as in Spiranthes. Even the bark and wood of trees is often disposed spirally. This is very noticeable in some firs, and in the bark of the sweet chestnut (Castanea), of Thuja occidentalis, and other trees. The knaurs or excrescences which are sometimes found on the roots or stems of trees afford other illustrations of this universal tendency. These bodies consist of a number of embryo buds, which, from some cause or other, are incapable of lengthening. On examination every rudimentary or undeveloped bud may be seen to be surrounded by densely crowded fibres arranged spirally.

The axes of nearly all twining plants are themselves twisted, and twisted in a direction corresponding to the spontaneous revolving movement exhibited by these plants, as in the hop, the convolvulus, passion flower, &c., the degree of twisting being dependent to a great extent on the roughness of the surface around which the stem twines.

Considered as an exceptional occurrence, it occurs frequently in certain plants, and, when it affects the stem or branches, necessarily causes some changes in the arrangement of the parts attached to them; thus, spiral torsion of the axial organs is generally accompanied by displacement of the leaves, whorled leaves becoming alternate, and opposite or whorled leaves becoming arranged on one side of the stem only. Frequently also this condition is associated with fasciation, or, at least, with a distended or dilated state. An illustration of this in Asparagus has been figured at p. 14.

Very often the leaves are produced in a spiral line round the stem, as in a specimen of Dracocephalum speciosum described and figured by C. Morren. The leaves of this plant are naturally rectiserial and decussate, but, in the twisted stem the leaves were curviserial, and arranged according to the 5/13 plan. Now, referring to the ordinary notation of alternate leaves, we shall have the first leaf covered by the fifth, with two turns of the spiral; since decussate leaves result from two conjugate lines, the formula will be necessarily 2/5. The fraction 5/13 hence comes regularly into the 2/5 series (2/5, 3/8, 5/13). Thus, the leaves in assuming a new phyllotaxy, take one quite analogous to the normal one.

One of the most curious instances that have fallen under the writer's own observation occurred in the stem of Dipsacus fullonum. (See 'Proceedings of the Linnean Society,' March 6, 1855, vol. ii, p. 370). The stem was distended, and hollow, and twisted on itself; its fibres, moreover, were arranged in an oblique or spiral direction; the branches or leaf-stalks, which usually are arranged in an opposite and decussate manner, were, in this case, disposed in a linear series, one over the other, following the line of curvature of the stem. When the course of the fibres was traced from the base of one of the stalks, upward around the stem, a spiral was found to be completed at the base of the second stalk, above that which was made the starting point. Now, if opposite leaves depend on the shortened condition of the internode between the two leaves, then, in the teazel-stem just described, each turn of the spiral would represent a lengthened internode; and, if the fibres of this specimen could be untwisted, and made to assume the vertical direction, and, at the same time, the internodes were shortened, the result would be the opposition of the branches and the decussation of the pairs; this explanation is borne out by the similar twisting which takes place so frequently in the species of Galium and other Rubiaceæ.

G. Franc was one of the first to notice this twisting in Galium, and M. Duchartre, in mentioning a similar instance, gives the following explanation of the appearance which will be found to apply to most of these cases. In the normal stem of Galium Mollugo the branches are opposite in each verticil and crossed in the two successive ones. The stem is four-angled, each angle having a nerve. Each of these nerves, springing from the origin of a branch in one whorl, terminates in the interval which separates the point of origin of the two branches in the whorl next above it. In the deformed stem one of the nerves corresponds to the insertion of a branch, its neighbour is in the adjoining vacant space; hence it results that four nerves correspond to two branches and to two consecutive interspaces, and hence the analogy between a single normal internode provided with its two branches and its four nerves. What confirms this inference is that the nerve, which begins at the point of origin of a branch, after making one spiral turn round the stem, terminates in the interval that separates the two following branches, just as in a branch of the normal stem it ends in the upper whorl between the two next branches. The torsion, then, in this Galium caused the separation of the two opposite branches of the same verticil, and placed them one above another, and this being reproduced in all the whorls, all the branches come to be arranged on the same longitudinal line. The leaves are susceptible of the same explanation; they are inserted in groups of three or four in one arc round the origin of each branch. In the malformation each series or group of four leaves, with its central branch, is equivalent to half a whorl of the natural plant with its axillary branch. In other words, the malformation consists in a torsion of the stem, which separates each whorl into two distinct halves; these half-whorls, with their axillary branches, are placed on a single longitudinal series one above another. This case is quoted at some length, as it is an admirable example of a very common form of malformation in these plants.

In some parts of Holland where madder is cultivated a similar deformation is particularly frequent. The leaves, however, are not always grouped in the way in which they were described by M. Duchartre, but more commonly form a single continuous line; when arranged in leaf-whorls it generally happens that some of the leaves are turned downwards, while others are erect. It has been said that this condition occurs particularly frequently in plants growing in damp places. It is certainly true that spiral torsion of the stem is specially frequent in the species of Equisetum, most of which grow in such spots. In these plants either the whole of the upper part of the stem is thus twisted, or a portion only: thus Reinsch cites a case in Equisetum Telmateia, where the upper and lower portions of the stem were normal, while the intermediate portion was twisted spirally. In this instance the whorl next beneath the spiral had twenty-eight branchlets, and that immediately above it thirty. Along the course of the spire there were two hundred and three; dividing this latter number by the mean of the two preceding, it was seen that the spire included the constituents of seven ordinary verticils.

Here also may be mentioned a curious bamboo, the stem of which is preserved in the British Museum, and in which the internodes, on the exterior, and the corresponding diaphragms and cavities within are spiral or oblique in direction.

The root is also subject to the same malformation, the inducing cause being usually some obstruction to downward growth, as when a plant has been grown in a small pot, and becomes, as gardeners say, pot-bound.

The axial portion of the flower, the thalamus, is also occasionally twisted in a spiral direction, the lateral parts of the flower being in consequence displaced. Morren spoke of this displacement of the floral organs as "speiranthie."

Morren draws a distinction between spiral-torsion or spiralism and the less regular torsion spoken of in the preceding section; in the former case not only is the axis twisted, but its constituent fibres also. The condition in question in some cases seems to be inherited in the seedling plants.

The following is a list of the plants in which spiral torsion of the stem or branches has been most frequently observed. (See also under Fasciation and Contortion.)

• Hesperis matronalis.
• Dianthus barbatus.
• Pyrus Malus.
• torminalis.
• Cercis siliquastrum!
• Punica Granatum.
• Robinia pseudacacia!
• Rubia tinctorum.
• Dipsacus fullonum!
• pilosus.
• Gmelini.
• Scabiosa arvensis.
• *Valeriana officinalis!
• dioica!
• Galium aparine!
• *Mollugo!
• verum!
• Hippuris vulgaris!
• Veronica spicata.
• longifolia.
• Hyssopus officinalis.
• Thymus Serpyllum.
• Lamium purpureum!
• Dracocephalum speciosum.
• Mentha aquatica.
• Mentha viridis.
• Fraxinus vulgaris!
• Sambucus nigra.
• Zinnia.
• Phylica.
• Beta.
• Rumex, sp.
• Ulmus campestris.
• Casuarina rigida.
• Abies excelsa!
• Lilium Martagon!
• candidum.
• *Asparagus officinalis!
• Sagittaria sagittifolia.
• Epipactis palustris.
• Triticum repens!
• Lolium perenne!
• Phleum pratense.
• Juncus conglomeratus!
• Scirpus lacustris.
• Equisetum Telmateia.
• limosum.
• fluviatile.
• arvense!

Among the more important papers relating to this subject may be mentioned:

Moquin-Tandon, 'El. Ter. Veg.,' p. 181. Kros, 'De Spira in plantis conspicua.' Morren, 'Bull. Acad. Roy. Belg.,' 1851, tom. xviii, part i, p. 27. Milde, 'Nov. Act. Acad. Leop. Carol. Nat. Cur., 1839. Ibid., vol. xxvi, part ii, p. 429, Equisetum. Irmisch, 'Flora,' 1858, t. ii, Equisetum. Vrolik, 'Nouv. Mem. Instit. Amsterdam,' Lilium. Schlechtendal, 'Bot. Zeit.,' xiv, p. 69, et v, p. 66. De Candolle, 'Organ. Veget., t. i, p. 155, tab. xxxvi, Mentha, &c. Alph. de Candolle, 'Neue Denkschr. Allg. Schweiz. Gesellschft.,' band v, tab. vi, Valeriana. Duchartre, 'Ann. Sc. Nat.,' ser. 3, vol. i, p. 292. 'Gardeners' Chronicle,' July 5, 1856, p. 452, c. ic. xylogr., spiral branches from Guatemala—tree not known.

Spiral twisting of the leaf is scarcely of so common occurrence as the corresponding condition in the stem. In Alstrœmeria it occurs normally, as also in some grasses. In the variety annularis of Salix babylonica the leaf is constantly coiled round spirally. A similar contortion occurs in a variety of Codiæum variegatum lately introduced from the islands of the South Seas by Mr. J. G. Veitch.

Fern fronds are occasionally found twisted in the same manner, e.g. Scolopendrium vulgare var. spirale.

Adventitious tendrils.—Under ordinary circumstances tendrils may be described as modifications of the leaf, the stipule, the branch, or of the flower stalk, so that it is not a matter of surprise to find tendrils occasionally springing from the sepals or petals, as indeed happens normally in Hodgsonia, Strophanthus, &c.

M. Decaisne found a flower of the melon in which one of the segments of the calyx was prolonged into a tendril, and Kirschleger records a similar instance in the cucumber, while Mr. Holland ('Science Gossip,' 1865, p. 105) mentions a case in which one of the prickles on the fruit of a cucumber had grown out into a tendril.

In Cobæa scandens the foliar nature of the tendril is shown by the occasional presence of a small leaflet on one of the branches of the tendril, and a similar appearance may frequently be seen in Eccremocarpus scaber. On the other hand, in the vine, the axial nature of the tendril is revealed by the not infrequent presence of flowers or berries on them, as also in Modecca and some Passifloraceæ.

Darwin, speaking of the tendrils of Bignonia capreolata, says it is a highly remarkable fact that a leaf should be metamorphosed into a branched organ, which turns from the light, and which can, by its extremities, either crawl like a root into crevices, or seize hold of minute projecting points, these extremities subsequently forming cellular masses, which envelope by their growth the first fibres and secrete an adhesive cement.

Interrupted growth.—This term is here used in the same sense as in ordinary descriptive botany, as when an "interruptedly pinnate" leaf is spoken of. A similar alternation may be observed occasionally as a teratological occurrence, though it is not easy to account for it.

Fig. 175 shows an instance of the kind in a radish, and fig. 176 a similar deformity in the case of an apple, the dilatation of the flower-stalk below the ordinary fruit producing an appearance as if there were two fruits one above another.

In leaves this peculiar irregularity of development is more common.

In some varieties of Codiæum variegatum the leaves resemble those of Nepenthes, as the basal portion is broad, and terminates in a projecting midrib destitute of cellular covering, and this again terminates in a small pouch or pitcher. Somewhat similar variations may be found in ferns, especially Scolopendrium vulgare.

Instead of the pouch there is formed sometimes in the plant last mentioned a supplementary four-lobed lamina, the four lobes being in two different planes, and diverging from the midrib, so that the section would resemble [symbol: Sideways X], the point of intersection of the x representing the position of the midrib. This four-winged lamina is thus very similar to the four-winged filaments described and figured at p. 289, and to the leaf-like anther of Jatropha described by M. Müller, p. 255.

Cornute leaves (Folia cornuta).—The condition to which this term applies is that in which the midrib, after running for a certain distance, generally nearly to the point of the leaf, suddenly projects, often in a plane different from that of the leaf, and thus forms a small spine-like out-growth. Should this happen to be terminated by a second laminar portion, an interrupted leaf would be formed. In Scolopendrium vulgare and other ferns this condition has been noticed, as also in some of the varieties of Codiæum variegatum already referred to.

Flattening.—There are some plants whose stem or branches, instead of assuming the ordinary cylindrical form, are compressed or flattened; such are some species of Epiphyllum, Coccoloba, Bauhinia, &c. The same thing occurs in the leaf-like branches of Ruscus, the flower-stalks of Xylophylla, Phyllanthus, Pterisanthes. Martins proposes to apply the word 'cladodium' to such expansions, just as the term phyllodium is applied to the similar dilatation of the leaf-stalks. If we exclude instances of fasciation, i.e. where several branches are fused together and flattened, we must admit that this flattening does not occur very often as a teratological appearance.

Mr. Rennie figures and describes a root of a tree which had become greatly flattened in its passage between the stones at the bottom of a stream, and had become, as it were, moulded to the stones with which it came into contact.

The spadix of Arum, as also of the cocoa-nut palm, has been observed flattened out, apparently without increase in the number of organs.

When the blade of the leaf is suppressed it often happens that the stalk of the leaf is flattened, as it were, by compensation, and the petiole has then much the appearance of a flat ribbon (phyllode). This happens constantly in certain species of Acacia, Oxalis, &c., and has been attributed, but doubtless erroneously, to the fusion of the leaflets in an early state of development and in the position of rest.

In some water plants, as Sagittaria, Alisma, Potamogeton, &c., the leaf-stalks are apt to get flattened out into ribbon-like bodies; and Olivier has figured and described a Cyclamen, called by him C. linearifolium, in which, owing to the suppression of the lamina, the petiole had become dilated into a ribbon-like expansion—déformation rubanée of Moquin.

Chapter II. Polymorphy.

Usually the several organs of the same individual plant do not differ to any great extent one from another. One adult leaf has nearly the same appearance and dimensions as another; one flower resembles very closely another flower of the same age and so on. Nevertheless it occasionally happens that there is a very considerable difference in form in the same organs, not only at different times, but it may also be at the same time. Descriptive botanists recognise this occurrence in the case of leaves, and apply the epithet heterophyllous to plants possessed of these variable foliar characters. In the case of the flower, where similar diversity of form occasionally exists, the term dimorphism is used.

As these phenomena appear constantly in particular plants, they are hardly to be looked on, under such circumstances, as abnormal, but where they occur in plants not usually polymorphic, they may be considered as coming within the scope of teratology.

Heterophylly.—As a general rule, the leaves or leaf-organs in each portion of a plant, from the rhizome or underground axis, where it exists, to the carpellary leaf, have their own special configuration, subject only to slight variations, dependent upon age, conditions of growth, &c. The cotyledons are very uniform in shape in each plant, and are scarcely ever subject to variation. The leaves near the base of the stem, the root-leaves as they are not unfrequently called, sometimes differ in form from the stem-leaves; these again differ from the bracts or leaves in proximity to the flower. The floral envelopes themselves, as well as the bud-scales, all have their own allotted form in particular plants, a form by which they may, in most cases, be readily recognised. Hence, then, in the majority of plants there is naturally very considerable difference in the form of the leaf-organs, according to the place they occupy and the functions they have to fulfil; but, in addition to this, it not unfrequently happens that the leaf-organs in the same portion of the stem are subject to great variation in form. This is the condition to which the term heterophylly properly applies. The variation in form is usually dependent on a greater or less degree of lobing of the margin of the leaf; thus, in the yellow jasmine, almost every intermediate stage may be traced from an ovate entire leaf to one very deeply and irregularly stalked. Broussonettia papyrifera, and Laurus Sassafras, and the species of Panax, may be mentioned as presenting this condition. Sometimes in the last-named genus, as also in Pteridophyllum, every gradation between simple and compound leaves may be traced. The horse-radish (Cochlearia Armoracia) may also be instanced as a common illustration of polymorphism in the leaves. In ferns it is likewise of frequent occurrence, markedly so in Scolopendrium D'Urvillei, in which plant every gradation from a simple oblong frond to an exceedingly divided one may be found springing from the same rhizome at the same time.

A similar protean state, but little less remarkable, occurs in many of our British ferns, notably in Scolopendrium vulgare, of which Mr. Moore enumerates no fewer than 155 varieties, many of the forms occurring on the same plant at the same time. Cultivators have availed themselves of this tendency to produce multiform foliage, not only for the purposes of decoration or curiosity, as in the many cut-leaved or crisped-leaved varieties, but also for more material uses, as, for instance, the many varieties of cabbages, of lettuces, &c. Most of these variations are mentioned under the head of the particular morphological change of which they are illustrations.

The effect of a change in the conditions of growth in producing diversity in the form of the leaf may be here alluded to. Ficus stipulata, a plant used to cover the walls of plant-stoves in this country, and growing naturally on walls in India, like ivy, produces leaves of very different form, size, and texture, when grown as a standard, from what it does when adhering to a wall. Marcgraavia umbellata furnishes another example of a similar nature, as indeed, to a less extent, does the common ivy.

Allusion has been already made to the occasional persistence of forms in adult life, which are commonly confined to a young state, as in the case of some conifers which present on the same plant, at the same time, two different forms of leaves. Mention has also been made of the presence of adventitious buds on leaves and in other situations. The leaves that spring from these buds are usually of the same form as the other leaves of the plant, but now and then they differ. Of this a remarkable illustration is afforded by a fern, Pteris quadriaurita, in which the fronds emerging from an adventitious bud are very different from the ordinary fronds.

Dimorphism.—This term, applied specially to the varied form which the flowers or some of their constituent elements assume on the same plant, is an analogous phenomenon to what has been above spoken of as heterophylly, and, like it, it cannot, except under special circumstances, be considered as of teratological importance. A few illustrative cases, however, may here be cited.

Sir George Mackenzie describes a variety of the potato (Solanum tuberosum), which produces first double and sterile flowers, and subsequently single fertile ones; the other portions of the plant do not differ much.

Stackhousia juncea, according to Clarke, has mixed with its perfect flowers a number of apetalous blossoms destitute of anthers.

This peculiarity is well exemplified in the tribe Gaudichaudieæ of the order Malpighiaceæ. A. de Jussieu, in his monograph, speaks of these flowers as being very small, green, destitute of petals, or nearly so, with a single, generally imperfect anther; the carpels also are more or less imperfect, but not sufficiently so to prevent some seeds from being formed. A similar production of imperfect flowers has been noticed in many other orders, e.g. Violaceæ, Campanulaceæ, &c. In some cases these supplementary blossoms are more fertile and prolific in good seeds than are the normally constructed flowers. M. Durieu de Maisonneuve alludes to a case where flowers of this description are produced below the surface of the ground. The plant in question is Scrophularia arguta, and it appears that towards the end of the summer the lowest branches springing from the stem bend downwards, and penetrate the soil; the branches immediately above the lowest ones also bend downwards, but do not always enter the earth. These branches bear fertile flowers: those which are completely below the soil are completely destitute of petals; those which are on the surface have a four-lobed corolla whose divisions are nearly equal, like those of Veronica.

To Sprengel, and specially to Darwin, physiologists are indebted for the demonstration of the relation of di- and trimorphic flowers to fertilisation. In certain genera of orchids, such as Catasetum, &c., flowers of such different form are produced that botanists, without hesitation, considered them as belonging to different genera, until the fact of their occasional production on the same plant showed that they were not of even specific importance. It was reserved for Mr. Darwin to show experimentally that these very different flowers are really sexual forms of one and the same species, ordinarily occurring on different plants, i.e. diœcious, but occasionally formed on the same spike. The same excellent observer has demonstrated that the di- and trimorphic forms of Primula, of Linum, Lythrum, and other plants—forms differing mainly in the relative length of the stamens and styles, are also connected with striking differences in the number of perfect seeds produced. The most perfect degree of fertility is obtained when the stigma of one form is fertilised by the pollen taken from stamens of a corresponding height. On the other hand, when the union is, as Mr. Darwin states, illegitimate, that is, when the pollen is taken from stamens not corresponding in length to the style, more or less complete sterility ensues in the progeny, sometimes even utter infertility, such as happens when two distinct species are crossed, so that, in point of fact, the offspring of these illegitimate unions correspond almost precisely to hybrids.

Mere variations of form arising from hybridisation or other causes hardly fall within the limits of this work, though it is quite impossible to say where variations end and malformations begin. There are, however, two or three cases cited by Mr. Darwin from Gallesio and Risso to which it is desirable to allude. Gallesio impregnated an orange with pollen from a lemon, and the fruit borne on the mother tree had a raised stripe of peel like that of a lemon both in colour and taste, but the pulp was like that of an orange, and included only imperfect seeds. Risso describes a variety of the common orange which produces "rounded-oval leaves, spotted with yellow, borne on petioles, with heart-shaped wings; when these leaves fall off they are succeeded by longer and narrower leaves, with undulated margins, of a pale green colour, embroidered with yellow, borne on foot-stalks without wings. The fruit whilst young is pear-shaped, yellow, longitudinally striated and sweet; but, as it ripens, it becomes spherical, of a reddish-yellow, and bitter."

Sports or bud variations.—These curious departures from the normal form can only be mentioned incidentally in this place, as they pertain more to variation than to malformation.

The occasional production of shoots bearing leaves, flowers, or fruits of a different character from those found on the normal plant, is a fact of which gardeners have largely availed themselves in the cultivation of new varieties. The productions in question have been attributed to various causes, such as cross-breeding, grafting, budding, dissociation of hybrid characters, or reversion to some ancestral form, all of which explanations may be true in certain cases, but none of them supply the clue to the reason why one particular branch should be so affected, and the rest not; or why the same plant, at the same time, as often happens in Pelargoniums, should produce two, three, or more "sports" of a different character.

These bud variations may be perpetuated by grafts or by cuttings, sometimes even by seed. With reference to cuttings a curious circumstance has been observed, viz., that if taken from the lower part of the stem, near the root, the peculiarity is not transmitted, but the young plant reverts to the characters of the typical form (Carrière). This circumstance, however, is not of universal occurrence.

For further particulars on this interesting subject the reader is referred to Darwin's 'Variation of Animals and Plants,' i, p. 373, where numerous references are given, and wherein certain well-known and highly remarkable instances, such as the Cytisus Adami, the trifacial orange, &c., are discussed.

Chapter III. Alterations of Colour.

Changes in the colour of the several organs of plants are more often either pathological or the result of variation than of malformation properly so called.

Alterations in colour arise from a diminished or an increased amount of colouring matter, or from an unusual distribution of the solid or fluid matters on which the colour depends. The superposition of cells containing colouring material of different tints produces naturally a very different set of hues from those which are manifested when the colours are not blended. Referring the reader to the ordinary text-books on vegetable physiology and chemistry for details as to the nature and disposition of colouring materials in plants under natural circumstances, it will only be necessary to cite a few instances of deviation from the general colour of plants or their organs.

Albinism.—This change is due to the deficient formation of green colouring matter or chlorophyll, and is more a pathological condition than a deformity.

It seems necessary to draw a distinction between this state and ordinary blanching or etiolation. In the former case chlorophyll seems never to be formed in the affected parts, even if they be exposed to light, while an etiolated organ, when placed under favorable circumstances, speedily assumes a green colour. In Richardia æthiopica one or more leaves become occasionally as white as the spathe is usually.

Virescence.—Engelmann pointed out that, so far as flowers were concerned, there are two ways in which they assume a green colour, either by a simple development of chlorophyll in place of the colouring matter proper to the flower, or by an actual development of leaf-like organs in the room of the petals—frondescence. Morren judiciously proposed to keep these two conditions separate, calling the one virescence, the other frondescence (see p. 241).

Many of the cases recorded as reversions of the parts of the flower to leaves are simply instances of virescence; indeed, it is not in all cases easy to distinguish between the two states. The examination of the arrangement of the veins is often of assistance in determining this point; for instance, if, under ordinary circumstances, the venation of the petal be such as is characteristic of the sheath of the leaf, while in the green-coloured flower of the same species the venation is more like that which belongs to the blade of the leaf, the inference would, of course, be that the green colour was due to frondescence or phyllody.

The persistence or duration of petals is often increased when they are subject to this change; instead of falling off speedily they become persistent when so affected.

Some flowers are more liable to virescence than others. The common honeysuckle, Lonicera Periclymenum, is one of these, and it is noticeable in this plant that the calyx remains unaffected—a circumstance which Morren says shows the distinctness of virescence from frondescence; for, in this instance, we have the most foliaceous portion of the flower remaining unchanged, while the corolla and other organs, usually less leaf-like in their nature, assume a green colour; but this may rather be attributed to the axial nature of the so-called adherent calyx. The stamens in these green-flowered honeysuckles are usually green also, but with abortive anthers, and the pistil also is in a rudimentary condition. Umbelliferæ are not unfrequently subject to this change, e.g., Torilis Anthriscus, Daucus Carota, Heracleum Sphondylium, Carum carui, &c. Primulaceæ, again, are frequently subject to virescence. Among Compositæ the following species are recorded as having had green flowers—Cirsium tricephalodes, Senecio vulgaris, Calendula officinalis, Pyrethrum Parthenium, Carduus crispus, Hypochæris radicata, Hieracium prealtum, Cirsium arvense, Coreopsis Drummondi. In Ranunculaceæ virescence has been observed in Delphinium elatum, crassicaule and Ajacis, Anemone hortensis and nemorosa, Aquilegia vulgaris, Ranunculus Philonotis.

Many of these cases, and others that might be cited, are probably instances of frondescence or phyllody (see p. 241).

Chromatism.—This term is here intended to apply specially to those cases in which any organ of a plant assumes a colour approximating to that of the petals, or in which the normal green is replaced by tints of some other colour. To a certain extent the change in question is the same as that spoken of under the head of petalody (see p. 283), but there are cases in which, while the ordinary situation and form are those of leaves, the coloration is that of the petals. Such was the case in the Gesnera mentioned by Morren (see p. 88), and in which a leaf occupied the position of an inflorescence, and became brightly coloured. In tulips the presence of a highly coloured leaf on the flower-stalk, below the flower, is not uncommon. So also the bracts or leaves below the perianth in Anemone coronaria and hortensis not unfrequently assume the coloration usually confined to the parts of the perianth. A similar illustration has presented itself, as this sheet is passing through the press, in which two of the leaflets of the compound leaf of a rose were brightly coloured like the petals, the others being of their ordinary green colour.

The occurrence of coloured bracts, as in Poinsettia, Bougainvillea, &c., is very common under natural conditions, and need not here be further alluded to.

Increased intensity of colour often accompanies teratological changes; an instance has just been alluded to in the Gesnera; the feather hyacinth, Muscari comosum, furnishes another illustration, the adventitious pedicels being brightly coloured.

In fasciated stems, also, of herbaceous plants, it not unfrequently happens that the upper portions of the stem are brightly coloured.

The occurrence of flowers or fruits of different colours on the same plant, or even in the same cluster, is a phenomenon which does not come within the scope of the present book; the reader may, however, be referred to the excellent summary on this subject published by Mr. Darwin in his work on the 'Variation of Animals and Plants under Domestication.'