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 asci 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 theS. 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 

 TrK.^.saccHaromycestiiifsoMeui, which a. parietal layer of protoplasm remains at first 



R. (Wine-yeast). Formation of spores , , . ,_-,. , _. - 



in sprout-ceiis, taken from ferment- everywhere unbroken (rig. 122). 1 he spores soon form 



in? must and spread out for thirty- i i i i i 



six hours on a microscopic slide in dis- a. membrane which always remains thin, and increase 



tilled water. The spores are not yet . , , .. , i i , i 



fully formed. Magn. about 600 times, 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 



