150 



COMPARATIVE MORPHOLOGY OF FUNGI 



ogenous; these may still form processes; since many cells no longer take 

 part in copulation, however, these are forced to grow long distances; or 

 they grow past each other and no longer copulate. Exceptionally in 

 some cells, four spores may arise parthenogenetically, the other cells 

 may develop purely vegetatively. 



This life cycle of Schizomaccharomyces odosporus may be connected 

 directly to that of Endomyces fibuliger. In this species, two sprout cells 

 may copulate with each other; only in E. fibuliger one sprout cell becomes 

 an ascus, while in S. odosporus the sexual act is isogamous. Gametangial 

 copulation, which in Eremascus fertilis was the only form of sexuality 

 and in Endomyces fibuliger was partially replaced by pseudogamy 

 (copulation of two vegetative cells), in S. odosporus is entirely suppressed 



1 



8 



/^% 



ffc 



Fig. 92. — Schizosaccharomyces odosporus. Copulation and development of asci. (X 750; 



after Guillermond, 1903, 1905, 1917.) 



and replaced by pseudogamy. This also disappears, and the cells, after 

 unfruitful attempts at copulation, may change parthenogenetically to 

 asci or, without this attempted copulation, may develop asci directly 

 and vegetatively. 



In the other Schizosaccharomyceteae, sexuality and spore formation 

 degenerate still further. Thus in S. Pombe, the yeast of a negro beer, 

 and in S. Mellacei, a yeast occurring in the rum factories of Jamaica, 

 numerous asporogenous strains are known and in S. asporus, the yeast 

 of arak manufacture in Java, no spores are known. 



While in the Schizosaccharomyceteae, the fertilization has become 

 chiefly isogamous, in the Saccharomyceteae there appears a tendency 

 to heterogamy and pedogamy. The simpler forms, as Zygosaccharo- 

 myces Barkeri (Barker, 1901), Z. Priorianus and Willia anomala (Guiller- 

 mond, 1911a), like Schizosaccharomyces odosporus, may be connected 



