214 YEASTS AND MOLDS 
by such “ pseudoscientific’”’ names as “ beer yeast,’ “wine yeast,” etc., 
or they may be even numbered. The taxonomist, however, must be 
concerned with keeping this group of fungi classified and so far as pos- 
sible properly named. Many investigators have classified the budding 
fungi. Anderson (1917) has reviewed the various investigations and a 
student will find a good summary with discussion of the various classi- 
fications in his paper. 
Hansen has done most work on the classification of the yeasts. 
His classification which appeared in 1904 is now accepted as the basis 
for classification of the true yeasts. He made two families which 
are divided into nine genera. Not all of these have been accepted by 
microbiologists. Guillierimond (1912) does not recognize the schizo- 
saccharomycetes which Hansen separated from the saccharomycetes 
by the fact that they reproduced by fission. He divides the saccharo- 
mycetes into five groups. Hansen’s classification is as follows: 
K=uY TO GENERA OF TRUE YEASTS 
(Hansen after Buchanan) 
Family I. Vegetative reproduction by budding ...... Saccharomycetacese 
A. Cells do not form a surface membrane at 
once on sugar media, i.e., do not 
grow exclusively at the top of ibe 
medium. 
1. Spores having a single membrane. 
a. Cells fusing in pairs before 
spore formation ....... Zygosaccharomycete 
6. Cells not fusing in pairs before 
spore formation. 
(1) Spores germinate by or- 
dinary budding..... Saccharomyses 
(2) Spores germinate by 
means of promycel- 
TUM... eee ee eee Saccharomycodes 
2. Spores having two membranes. . . .Saccharomycopsis 
B. Cells forming a surface membrane at 
once by sugar media. 
1. Spores spherical, hemispherical or 
regular... ......0 ccc eee eee Pichia 
2. Spores lemon shaped with pointed 
CNS... eee ee cee eee ees Willia 
