284 YEASTS AND YEAST-LIKE FUNGI 



each, by which they are motile for a time. This disappears when 

 they germinate. Ashbya is a yeast very like Nematospora but the 

 flagellated spindle-shaped spores are formed in the mycelium. The 

 ascus is a part of the mycelium and thus the genus hardly belongs 

 to the Endomycetaceae. However, the similarity of Ashbya to 

 Nematospora makes it desirable to consider it here. Coccidiascus 

 is parasitic on the fruit fly Drosophila. The vegetative cells are 

 round and they reproduce by budding. Eight spindle-shaped or 

 banana-shaped spores are formed. 



Asporogenous Yeasts. The asporogenous yeasts, that is, those 

 which do not produce ascospores, are a heterogenous group. Some 

 seem to be derived from Basidiomycetes, others from Ascomycetes. 

 We shall first consider the larger group, those probably derived from 

 Ascomycetes. Some may be strains resulting from union of haploid 

 cells derived from the same ascospore as suggested by Lindegren and 

 Lindegren.^°' ^-' ^^ Those are known to form spores with difficulty and 

 it is quite probable that this power may be lost entirely with cultiva- 

 tion. The loss of spore formation may be a form of degeneration 

 resulting from cultivation. Long-cultured strains of yeasts frequently 

 lose their ability to form spores readily. Also it is possible that some 

 of them are haploid forms of heterothallic yeasts. Winge and Laust- 

 sen, in investigating this possibility, tried to make crosses with all 

 the asporogenous yeasts they could obtain, and got no spores. Still 

 it remains a possibility. It has occurred to us that since intergeneric 

 hybrids are usually sterile, the asporogenous yeasts in some cases 

 may be such naturally occurring hybrids continuing to multiply 

 vegetatively as diploid cells, i.e., they are sterile hybrids. Many 

 asporogenous species have the size and vigor of diploid cells. 



All the asporogenous yeasts probably derived from the Ascomy- 

 cetes may be included in two families, Cryptococcaceae (Torulop- 

 sidaceae) and Nectaromycetaceae of the Fungi Imperfecta Lodder " 

 excludes yeasts forming true mycelium, but includes those forming 

 pseudomycelium, a distinction difficult to make in practice, and one 

 which Stelling-Dekker avoided by including both types in her system 

 of sporogenous yeasts. The family Cryptococcaceae is divided into 

 two subfamilies, the Cryptococcoideae (Torulopsidoideae) , including 

 those yeasts with no, or only primitive, pseudomycelium and the 

 Candidoideae (Mycotorulbideae) which form pseudomycelium (and 

 often true mycelium in fact) . 



The following key shows the relationship of the asporogenous 

 yeasts. 



