CLASSIFICATION OF YEASTS 275 



Subgenus PICHIA sensu stricto. Spores parthenogenetic. 

 Subgenus ZYGOPICHIA. Spores by isogamous or heterogamous 

 conjugation. 



Genus IV. HANSENULA. Cells oval or long cylindrical. Seldom 



round. Pseudomycelium formed. Spores parthenogenetic or 



by isogamous conjugation, hemispherical or spherical with a 



band, 2 to 4 per ascus. Oxidative. Nitrates reduced. 



Subgenus HANSENULA sensu stricto. Spores parthenogenetic. 



Subgenus ZYGOHANSENULA. Spores by isogamous conjugation. 



Genus V. DEBARYOMYCES. Round, occasionally oval cells, at 

 times pseudomycelium. Spores by isogamous, more frequently 

 heterogamous, conjugation, round, more or less warty, 1 to 2 

 per ascus. Most species exclusively oxidative, some also fer- 

 mentive. 



Genus VI. SCHWANNIOMYCES. Cells oval. Spores formed after 

 unsuccessful attempts at conjugation, round, warty, banded, 

 1, rarely 2, per ascus. Dominantly fermentive. 

 Tribe c. NADSONIEAE. Growth forms yeast cells, occasionally pseudo- 

 mycelium, no true mycelium. Multiplication by bipolar bud- 

 ding. Buds with a broad base. Spores parthogenetic or by 

 heterogamous conjugation. 



Genus I. SACCHAROMYCODES. Cells lemon-shaped or sausage- 

 shaped. Vegetative reproduction by combination of budding 

 and fission. Spores parthenogenetic, round, smooth, 4 per 

 ascus. Spores conjugate upon germinating. Both oxidative 

 and fermentive. 



Genus II. HANSENIASPORA. Cells lemon-shaped. Spores partheno- 

 genetic, round, or hat-shaped, 2 to 4 per ascus. Both oxidative 

 and fermentive. 



Genus III. NADSONIA. Cells egg to lemon-shaped. Vegetative re- 

 production by a combination budding and fission. Spores 

 heterogamous. After fusion of nuclei of mother cell and bud, 

 a new bud is formed which becomes the ascus. Spores round, 

 warty, 1 per ascus. Both oxidative and fermentive. 



Genus IV. ZYGOSACCHAROMYCODES. Cells oval. Vegetative 

 reproduction by combination of budding and fission. Spores 

 by isogamous conjugation or, rarely, parthenogenetic. Spores 

 round, 1 to 4 per ascus. 

 Subfamily D. NEMATOSPOROIDEAE. Growth forms both mycelium and 

 yeast cells. Multiplication by multipolar budding. Spores 

 formed by isogamous conjugation or parthenogenetically. 

 Spores needle-shaped or fusiform, with or without flagella. 

 Both oxidative and fermentive. 



Genus I. MONOSPORELLA. Cells oval. Spores parthenogenetic, 

 needle-like, 1 per ascus. 



Genus II. NEMATOSPORA. Cells oval, elongated, irregular, or 

 mycelium-like. Spores parthenogenetic, fusiform, flagel- 

 lated, 2 to 8 per ascus. Both oxidative and fermentive. 



Genus III. COCCIDIASCUS. Round to oval cells, spores by isoga- 

 mous conjugation, fusiform, 8 per ascus. Entirely oxidative. 



