288 YEASTS AND YEAST-LIKE FUNGI 



This probably varies with the amount of iron occurring as impurities. 

 Very faint traces of iron are sufficient to produce the color. This 

 yeast may be easily distinguished from the common yeasts of the 

 genus Rhodotorula by the color. It is maroon rather than pink or 

 coral, and is not a carotinoid. Moreover, this yeast is fermentive 

 in contrast to Rhodotorula species. In old cultures the cells develop 

 very large fat globules which distend the cells and change its form 

 from oval to round. See Fig. 113/. Beijerinck states that this yeast 

 may be commonly found on grapes. It has been frequently isolated 

 from other sources as well, but is probably not very common. Being 

 so noticeable when growing on agar plates it is likely to attract at- 

 tention and to be isolated. Punkari and Henrici have made extensive 

 studies on variations of this yeast, and Roberts is now working on 

 this problem. Pseudomycelium is produced by rough variants. 



Recently Windisch -^ has described ascospore formation in C. 

 pulcherrimus and Roberts -■* has also demonstrated them. Spores 

 are found only in old and dried cultures and are not numerous. 

 Castelli^ was unable to find spores and one of us could not find 

 them after tedious search in a stock culture. We are convinced that 

 ascospores are really formed by some strains, at least, but it is evi- 

 dent that workers cannot depend upon them for diagnosis. And 

 since Roberts after extended and careful work was unwilling to assign 

 this species ta a perfect genus, we also shall classify it among the 

 asporogenous yeasts. 



The so-called black yeasts were discussed on page 111. 



Since species of Cryptococcus are so frequently isolated, and since 

 some of them are of some importance, the following key, largely 

 derived from Lodder,"- " is given. It should be emphasized that 

 every effort should be made to induce sporulation before placing an 

 isolate in the genus Cryptococcus. 



KEY TO THE SPECIES OF CRYPTOCOCCUS * 



(Adapted from Lodder) 

 1. No sugars fermented, 

 a. Nitrates utilized. 



I. Agar slant cultures mucoid. 



A. Cells round, or slightly oval. Agar slant cultures yellowish. 



C. alhidus 



B. Cells round in wort, oval in agar. Cultures tinged with red. 



C. rotundatus 

 II. Agar slant cultures not mucoid. C- aerius 



* New combinations are pubUshed elsewhere. 



