38o 



FUNGI 



become asci. In the latter case either certain cells become asci while 

 others remain sterile or the whole body of hyphse form asci. In E. 

 alnitorquus (Sadeb.) these asci have a pedicel-cell ; in E. aureus (Sadeb.) 

 there is nothing but asci left at maturity. When the ascospores ger- 

 minate they give rise to a yeast-like sprouting. 



3. Saccharomyces (Meyen). — The species of Saccharomyces occur 

 in fermenting substances, and are well known from theirpower of convert- 

 ing sugar into alcohol and carbonic acid. Among the familiar species- 

 are S. cerevisise (Meyen) 

 (ordinary yeast), S. el- 

 lipsoideus (Reess), S. 

 Pastorianus (Reess), al- 

 coholic ferments which 

 are apparently mere form- 

 species. With these 

 should be placed S. My- 

 coderma of Reess, and 

 Chalara Mycoderma of 

 Cienkowski ; and the 

 'thrush' fungus S. albi- 

 cans (Reess), which lives 

 parasitically on the mu- 

 cous membrane of the 

 human digestive organs, 

 but is also capable of ex- 

 citing a feeble alcoholic 

 fermentation in sugar 

 solutions. With the ex- 

 ception of the last-men- 

 tioned forms in which 

 hyphae occur, the species 

 of Saccharomyces are 

 unicellular fungi which 

 increase by sprouting. 

 The cells, in which a nucleus has not been demonstrated, are round or 

 oval in form, and the sprouting takes place in the form of a pro- 

 tuberance, which gradually swells and becomes constricted and finally 

 cut off by a wall at the point of origin. These new cells either separate 

 at once, or chains or groups remain united as they have been formed. 

 When such cells are cultivated, on the cut surface of a potato for 

 example, certain cells may form asci, each containing two to four 

 ascospores. These are at once capable of germination, which takes 



Fig. 313. — Saccharomyces cerevisim Meyen. a, single cell 

 of beer-yeast ; 3, c, stages of sprouting : d^ colony of sprout- 

 cells : f, cell with four ascospores ; f^ one with two ; g^ group 

 of ascospores with one sprouting ; A, further development of 

 a similar group (Jt x 750, the others much more), (e — A 

 after Reess.) 



