268 DIVISION II.—COURSE OF DEVELOPMENT OF FUNGI. 
year and which consist entirely of the sprouts of S. Cerevisiae. But a certain number 
of known species also forms spores in ascı under certain conditions ; this fact was dis- 
covered by DeSeynes in Saccharomyces Mycodermain, 1868, was afterwards examined 
more thoroughly especially by Reess, and has now been certainly established in S. 
Mycoderma and the forms included under the names of S. Cerevisiae, S. ellipsoideus 
and S. Pastorianus. It occurs most readily and most frequently in the S. ellipsoideus 
of wine-yeast. It has been studied by Reess, Hansen, and other observers in S. 
Cerevisiae, but it is often difficult to induce this cultivated form to produce spores. 
Spores begin to be formed if well-fed specimens, protected as far as possible from 
invasion by other Fungi and Schizomycetes, are kept without food or restricted to the 
least possible amount of it in presence of water and air containing free oxygen and 
in a suitable temperature; if, for example, yeast is spread in a thin layer on moist 
surfaces, such as succulent parts of plants, plaster of Paris, or a microscopic slide, or 
kept in a little distilled water. At first new cells are formed by sprouting in such 
cultures at the expense of the old ones, which may become exhausted and sometimes 
die. Then spores are formed in cells which are not distinguished by their origin, 
shape, or any other particular, sometimes in a few isolated cells, at other times in all 
or most of the cells of a chain. Two or four, or some- 
times three, seldom more than four spores are formed in 
a cell according to its size. The stages observed in the 
formation of the spores correspond to the processes 
known to occur in asci (see section XIX). The young 
spores appear simultaneously as delicately circumscribed 
round bodies of homogeneous protoplasm collected into 
a group inside the protoplasm of the mother-cell, in 
FiG.122. Sacchavomyceseltipsoideus, Which a parietal layer of protoplasm remains at first 
R. (Wine-yeast). Formation of spores n 
E man ulm ee everywhere unbroken (Fig. 122). The spores soon form 
six hours on a microscopic slide in dis. a Membrane which always remains thin, and increase 
fully formed. Magn about wotimer in volume while the protoplasm more or less completely 
disappears. When full-grown they may just fill the cavity of 
the mother-cell, but generally they do not quite fill it; if they are four in number they 
are disposed tetrahedrally as quadrants of a sphere or in a row according to the shape 
of the cell. They are now arrived at maturity. In older specimens the membrane of the 
mother-cell often collapses and disappears; it is ruptured according to Cienkowski’s 
account in Saccharomyces Mycoderma and releases the spores. The ripe spores can 
germinate as soon as they enter the nutrient fluid. In germination they swell slightly 
and form vacuoles, and then begin to sprout in the manner proper to each species ; 
the membrane of the mother-cell is broken through as the first sprouts are extruded. 
E. Hansen found in the species which he examined sprout-cells which were 
divided by thick flat partition-walls into 2-4 daughter-cells, and these cells germinated 
in the same way as the ascogenous spores, but he did not see the formation of these 
septa. Meanwhile, judging from the figures, we should be inclined to suspect that the 
formations in question are simply asci with their walls much collapsed after ripening 
and with the spores closely pressed one against another. 

The foregoing brief account of the formation of the spores of the Saccharomycetes 
is taken from Reess’ earlier statements and a recent revision of them in examining 
