Book I. Deviations from the Ordinary Arrangement of Organs (part 2)

M. Carrière has also recorded a curious circumstance with reference to the fastigiate variety of the false acacia Robinia pseudacacia; he states that if a cutting or a graft be taken from the upper portion of the tree, the fastigiate habit will be reproduced, and the branches will be furrowed and covered with short prickles; but if the plant be multiplied by detaching portions of the root-stock, then instead of getting a pyramidal tree with erect branches, a spreading bushy shrub is produced, with more or less horizontal, cylindrical branches, destitute of prickles.

Eversion of the axis.—In the case of the fig, the peculiar inflorescence is usually explained on the supposition that the termination of the axis becomes concave, during growth, bearing the true flowers in the hollow thus formed. The cavity in this case would probably be due not to any real process of excavation, but to a disproportionate growth of the outer as contrasted with the central parts of the fig. Some species of Sempervivum have a similar mode of growth, so that ultimately a kind of tube is formed, lined by the leaves, the central and innermost being the youngest. The hip of the Rose may be explained in a similar manner by the greater proportionate growth of the outer as contrasted with the central portions of the apex of the flower-stalk. In cases of median prolification, already referred to, the process is reversed, the central portions then elongate into a shoot and no cavity is formed. A fig observed by Zuccarini (figs. 105, 106) appears to have been formed in a similar manner, the flower-bearing summit of the stalk not being contracted as usual, the flowers projected beyond the orifice of the fig. If this view be correct the case would be one rather of lengthening of the axis than of absolute eversion since it was never inverted.

Altered direction of leaves.—The leaves partake more or less of the altered direction of the axis, as in fastigiate elms, but this is not universally the case, for though the stem is bent downwards the leaves may be placed in the opposite direction; thus in some specimens of Galium Aparine growing on the side of a cliff from which there had been a fall of chalk, the stems, owing apparently to the landslip, were pendent, but the leaves were abruptly bent upwards.

One of the most singular instances of an inverted direction of the leaves is that presented by a turnip (fig. 107) presented to the Museum of King's College, London, by the late Professor Edward Forbes. The turnip is hollow in the interior and the majority of the leaves springing from its apex instead of ascending into the light and air become bent downwards so as to occupy the cavity, and in such a manner as to bring to mind the position of an inverted embryo in a seed.

Altered direction of the flower and its parts.—The changes which take place in the relative position either of the flower as a whole or of its several parts during growth are well known, as also are the relations which some of these movements bear to the process of fertilisation, so that but little space need here be given to the subject beyond what is necessary to point out the frequent changes of direction which necessarily accompany various deviations from the ordinary form and arrangement of parts.

In cases where an habitually irregular flower becomes regular, the change in form is frequently associated with an alteration in direction both of the flower as a whole and, to a greater or less extent, of its individual members, for instance of Gloxinia, the normal flowers of which are irregular and pendent, there is now in common cultivation a peloriate race in which the flowers are regular in form and erect in position.

Fig. 108 shows the usual irregular form of Gloxinia, with which may be contrasted figs. 109, 110 and 111.

Fig. 109 shows the regular erect form; fig. 110 the calyx of the same flower; while in fig. 111 are shown the stamens and style of the two plants respectively. In the upper figure the style of the peloriate variety is shown as nearly straight, and the stamens undergo a corresponding change. No doubt the relative fertility and capacity for impregnation of the two varieties is affected in proportion to the change of form. The Gloxinia affords an instance of regular congenital peloria in which the regularity of form and the erect direction are due to an arrest, not of growth, but of development, in consequence of which the changes that ordinarily ensue during the progress of the flower from its juvenile to its fully formed condition do not take place.

A similar alteration accompanies this form of peloria in other flowers (see Peloria). A change in direction may result also from other circumstances than those just alluded to. Abortion or suppression of organs will induce such an alteration; thus in a flower of Pelargonium now before me three of the five carpels, from some cause or other, are abortive and much smaller than usual, and the style and the beak-like torus are bent downwards towards the stunted carpels instead of being, as they usually are, straight.

Amongst orchids, where the pedicel of the flower or the ovary is normally twisted, so that the labellum occupies the anterior or inferior part of the flower, it frequently happens, in cases of peloria and other changes, that the primitive position is retained, the twist does not take place, and so with other resupinate flowers. In Azaleas a curious deflexion of the parts of the flower may occasionally be met with. Fig. 112 shows an instance of this in which the corolla, the stamens and the style were abruptly bent downwards: as young flowers of this singular variety have not been examined it is difficult to form an opinion as to the cause of this variation. In one plant the change occurred in connection with the suppression of all the flowers but one in the cluster, or rather the place of the flowers was occupied by an equal number of leafy shoots.

Moquin mentions a flower of Rosa alpina in which two of the petals were erect, while the remaining ones were much larger and expanded horizontally. The same author quotes from M. Desmoulins the case of a species of Orobanche, in which a disjunction of the petals constituting the upper lip took place, thus liberating the style and allowing it to assume a vertical direction.

M. Carrière has described an instance wherein two apples were joined together, a larger and a smaller one; the former was directed away from the centre of the tree as usual, while the smaller one was pointed in exactly the opposite direction. The larger fruit had the customary parchment-like carpels, the smaller was destitute of them.

Sometimes the direction assumed by one flower as an abnormal occurrence is the same as that which is proper to an allied species or genus under natural circumstances; thus flowers of the vine (Vitis) have been met with in which the petals were spreading like a star (fleurs avalidouires), as in the genus Cissus.

Morren describes a curious condition in some flowers of Cuphea miniata, in which the placenta protruded through an orifice in the ovary, and losing the horizontal direction became erect (figs. 113, 114). A similar occurrence happened in Lobelia erinus. To this condition the Belgian savant gave the name of gymnaxony.