148 COMPARATIVE MORPHOLOGY OF FUNGI 



(Fig. 91, 3 to 5). After repeated nuclear division, the spores germinate 

 within the intermediate substance by germ tubes which usually proceed 

 again to conidial formation. The complete evacuation of the ascus is 

 only effected by the stipe cell beneath developing to a new ascus; in 

 proportion as this new structure bulges upward, the remainder of the 

 spore mass is pushed out. This sporangial proliferation may be repeated 

 up to twelve times; it is very reminiscent of the relationships of the 

 Saprolegniaceae where it is placed by Lohwag (1926). Unfortunately, 

 the cytological details of the life cycle of this interesting species are still 

 insufficiently known; possibly it develops parthenogenetically (Brefeld, 

 1891; Popta, 1899; Lohwag, 1926). 



Saccharomycetaceae. — The yeasts may be regarded as direct deriva- 

 tive of the Endomycetaceae in which the growth of the thallus by sprout- 

 ing has become entirely prevalent. Some forms, as Saccharomy codes 

 Ludwigii, Debaryomyces Kloeckeri, Ztjgosaccharomyces Priorianus and 

 Pichia membranifaciens, under certain conditions of nourishment, e.g., 

 on gelatin substrates, can still form true hyphae; these are unstable, 

 however, and with a slight alteration of the substrate break up into sprout 

 mycelia. 



The sprout cells are generally spherical or ellipsoidal, and hyaline, the 

 size varying according to substrate and age. Under unfavorable condi- 

 tions they can store fat and glycogen and surround themselves with a 

 double membrane. These resting cells are very resistent to environment 

 and can carry over unfavorable periods; probably they correspond to the 

 gemmae in Endomyces. At germination, the outer fragile wall is rup- 

 tured and the cells grow into a sprout mycelium. 



We may distinguish two tribes of the Saccharomycetaceae according 

 to the type of cell multiplication. In the Schizosaccharomyceteae, it 

 takes place as in Endomyces Magnusii: the cells elongate; when they have 

 attained a certain size they divide by septa into two daughter cells each, 

 which round off, separate, grow and divide similarly. These types are 

 chiefly of southern origin and at present only a few are known. In the 

 other group, the Saccharomyceteae, the sprout cells are formed, as in 

 Endomyces fibuliger, as small lateral protrusions of the mother cell; they 

 are abjointed, increase in size and finally attain the appearance of the 

 mother cell. This second tribe includes the greater part of the known 

 yeasts technically used as ferments. These two tribes are not as sharply 

 separated as would seem at first sight, thus Saccharomycodes Ludwigii 

 generally follows the first tribe but it may also increase by sprouting. 

 The sprouts are only formed at the poles, not at any spot as is usually 

 the case in yeasts. 



If the sprouting proceeds rapidly, the daughter cells may sprout fur- 

 ther (and in Schizosaccharomyces divide) before they are separated from 

 the mother cells. Thus there are formed small colonies and, in old cul- 



