44 



CYTOLOGY OF YEASTS 



have seen that the ascospores of the Schizosaccharomyces contain some 

 starch which collects in the wall. This substance replaces glycogen 

 and is used as a reserve during germination of the spores. Glycogen 

 appears in the cells from the beginning of fermentation and reaches its 

 maximum after 48 hours. It is almost always localized in the vacuoles 

 distinct from those which contain the metachromatic granules. 

 It diminishes gradually and disappears entirely towards the end of 

 fermentation. During sporulation it accumulates in great quantities 

 in the ascs and is absorbed by the ascospores during their maturity. 



C. Basophile Granules: These granules, very rare in young cells, 

 become very numerous in course of development, especially between 



12 and 24 hours. (Fig. 50, 5 and 8.) 

 They are not visible in the living cells 

 and do not take stains. For the most 

 part, they resist fixation and present 

 somewhat the same color characteristics 

 as the chromatin. They are stained 

 especially by hematoxylin which gives 

 them an intense black color like the 

 nucleus. This is less resistant and 

 they are easily decolorized. With the 

 other nuclear stains, they differentiate 

 themselves less closely from the nu- 

 cleus. These granules offer variable 

 shapes and dimensions. Many are 

 angular, and certain authors, as Hiero- 

 nymus and Kohl, have regarded them as crystalloids of protein. A 

 close examination, however, reveals that they are not crystalline. 



The basophile grains are probably albuminoid substances, but it 

 is not possible to state precisely their r61e. They are in all cases 

 substances of nutrition (reserve materials) and do not seem to have 

 a relation to fermentation, because they appear as well in yeasts 

 cultivated under aerobic conditions, as in yeasts in the process of 

 fermentation. On the other hand, they are numerous at the moment 

 of sporulation and contribute to the formation of the ascospores. 



D. Fats: These are present in the living cells under the form of 

 refractive granules of variable size, situated in the cytoplasm, and 

 are stained brown with osmic acid. Will has been able to color 

 them red by means of tincture of alkanna and has brought about 

 their dissolution by ether. Very abundant at the beginning of de- 

 velopment in certain species (Debar omyces globosus, Sch: occidentalis, 

 Torulaspora, Torula), these fat globules are absent or rather widely 

 distributed in other yeasts; especially the industrial varieties. In 



Fig. 50. Saccharomyces cerevisiae 

 in a Preparation Colored with 

 Ferric Hematozyline. 



1 to 4, beginning of fermentation; 5 to 8, be- 

 tween 12 and 24 hours; 9, after 48 hours. 



