CLASSIFICATION OF YEASTS 213 
daia should be carefully woiked out. All of this is necessary when 
comparing the new fungus to the described varieties. IIlustrations 
of the more common varieties have been included in this chapter. 
YEASTS 
The yeasts are fungi which cause many changes in food. Many of 
them are desirable changes while some are undesirable. For cen- 
turies they have played an important part in the domestic life of peoples 
and are the bases for great industries. Foods which have a high con- 
tent of carbohydrates are especially susceptible to the attack of yeasts. 
aoe 
OE 620 
SVE Ai 
Fig. 52.—Types of Cells in Common Yeasts. 
A, Saccharomyces cerevisve, B, Saccharomyces ellapsordeus; C, Mycodermai2nz (Adapted from 
Guilhermond’s Les Levures ) 
True and Pseudo Yeasts. True yeasts are budding fungi which 
produce endospores. The false yeasts resemble the true yeasts very 
closely but differ in the fact that no endospores are formed. These have 
some of the properties of the molds. The torule (Turpin), mycoderme 
(Persoona) and cryptococcus (Kiitzing-Vuillemin) and representatives 
of the false yeasts. 
Classification of Yeasts. The classification of the yeasts 1s rather 
confused. This is in part due to the different points from which the 
subject may be viewed. The fermentologist is concerned with the 
physiological changes which are brought about by yeasts and does not 
give much attention to nomenclature. His cultures may be designated 
