CHAPTER V.— COMPARATIVE REVIEW.—DOUBTFUL ASCOMYCETES. 267 
Four hemispherical spores are formed in each ascus, which escape when mature by 
the dissolution of the wall of the ascus, and put out germ-tubes in water. Nothing 
more is known of this species; the controversy which has arisen in the attempt to 
determine it will be noticed again in section XCIII. 
Section LXXVII. The chief representatives of the genus Saccharomyces 
are the Yeast-fungi which excite alcoholic fermentation and are known as Sac- 
charomyces Cerevisiae, S. ellipsoideus, S. Pastorianus, &c. These names, according 
to E. Hansen’s recent investigations, denote form-groups, which will no doubt have 
to be otherwise distributed. Besides these there are the Flowers of wine, S. Myco- 
derma, Reess, Cienkowski’s Chalara Mycoderma, and the Fungus of thrush (apthae), 
S. albicans, Reess, which grows as a parasite on the mucous membrane of the 
human digestive organs, but also thrives in saccharine fluids, where it excites a slight 
fermentation. The rest are found in quantity in or on fluids which are fermenting 
or have undergone fermentation. S. Cerevisiae is added intentionally to the wort of 
beer and is cultivated largely for this purpose. Other kinds and indeed S. Cerevisiae 
as well appear of themselves in must, finding their way into it chiefly from the 
surface of the juicy fruits which yield the must. 
They are conveyed to these fruits along with 
dust from the surfaces of other bodies (see be- 
low, section C). 
The larger part of these Fungi vegetate, 
as far as we know, only by sprouting (Fig. 121). 
Continuous branching hyphae with long seg- 
ments are found only in Saccharomyces 
albicans, in S. Mycoderma and Cienkowski’s 
Chalara; these grow directly, according to 
Cienkowski’s observations on S. Mycoderma, | FIG. 121. Saccharomyces Cerevisiae. a cells before 
sprouting. &—d cells sprouting in a fermenting saccharine 
from cells formed by sprouting, produce fresh ee ee development according to 
cells from their sides by sprouting, and ulti- 
mately divide transversely into short cells which then vegetate simply by sprouting. Other 
species, especially Reess’ S. Pastorianus, show a certain approach to this growth-form in 
that they are frequently chains of elongated sprout-cells, from which short cells are 
abscised laterally. The shape moreover of the single sprout varies generally between 
spherical and elongated cylindrical, with certain rules and limitations in each species. 
The cells that are formed one after another by sprouting in the fermenting fluid are 
usually at once separated from one another; connected strings of cells are to be seen 
when the plant vegetates on still surfaces, such as a microscopic slide especially, and 
the length and number of the chains vary according to the species. The cells of 
S. Cerevisiae, when developed in large quantities, often adhere together irregularly 
and form largish lumps, being attached to one another apparently by the muci- 
laginous outer lamellae of their membranes (see on page g). The structure 
of the sprout-cells is that of other vegetative fungal cells, but their membranes are 
comparatively thin and colourless. 
The Saccharomycetes in the sprouting form may be said to be capable of 
unlimited growth and multiplication if supplied with sufficient food. This is shown 
by the hundreds of thousands of pounds weight of yeast which are produced year by 

