Morphology of the Blastomycetes

The blastomycetes are composed of spherical or oval cells (8 to 9.5µ in diameter), which, when rapidly multiplying by budding, may form a spurious mycelium. A thin cell-wall encloses the granular protoplasm, in which vacuoles and sometimes a nucleus may be noted. This latter is best seen when stained with hæmatoxylin (see page 105).

During their growth and multiplication the blastomycetes split up solutions containing sugar into alcohol and CO2.

Saccharomyces (Fig. 81).—Note the round or oval cells of granular protoplasm (a) containing solid particles and vacuoles (c), and surrounded by a definite envelope.

Reproduction.—Budding; ascospores—asexual.

Note the asexual reproduction.

1. "Gemmation"—that is, the budding out of daughter cells (b) from various parts of the gradually enlarging mother cell. These are eventually cast off and in turn become mother cells and form fresh groups of buds.

2. Spore formation—"ascospores" (e). These are formed at definite temperatures and within well-defined periods; e. g., Saccharomyces cerevisiæ, thirty hours at 25° to 37°C., or ten days at 12°C.

Torulæ (Fig. 82).—Torulæ, whilst resembling yeasts in almost every other respect, never form endo-spores. Note the elongated, sausage-shaped cells (a) the larger oval cells (b) and the globular cells (c) the former two often interlacing and growing as a film.

Note the absence of ascospore formation.