1-H 



THE ASCOMYCETES 



to such genera as Geotrichum, Alycoderma, Candida, Castellania, 

 and Monilia, ^^•ith all of which the physician is more or less 

 familiar. 



Saccharomycetaceae. This family comprises the yeasts, first 

 described by Leemyenhoek in 1680. Althous^h fermentations 



Fig. 48. Various genera of yeasts. A. Saccharoiiiyces cerevisiae, showing 

 growth by budding and the formation of ascospores. B. Schizosaccharo- 

 viyces octosponis, with one cell undergoing fusion and two asci each con- 

 taining eight spherical ascospores. C. Saccharoniyces ellipsoideus, the wine 

 yeast. D. Ascus of Willia anoniala with derbv-hat-like ascospores. (From 

 Hansen.) E. Neviatospora pbaseoli, a single-appendaged ascospore and an 



eight-spored ascus. (From Wingard.) 



were carried out long before this time and scientific obseryers are 

 known to haye speculated on the nature of this process, the role 

 of yeasts was not definitely established until nearly 200 years 

 later as the result of Pasteur's researches. Much of present-day 

 knowledo-e of their physiologry and taxonomy has come from 

 the inyestigations of Hansen and of Guilliermond (1920). The 

 work of Henrici (1941) should be consulted by all who desire 

 an acquaintance with yeasts. 



Guilliermond (1920) recoo-nized 18 sfenera of yeasts. Yeasts 

 are characterized as fungi which multiply by buddingr or by 

 fission and also by forming sacs. Each cell may become an 



