154 



COMPARATIVE MORPHOLOGY OF FUNGI 



ciens, a wild yeast. With the disappearance of sexuality in many of 

 these forms, spore formation also disappears, and in them there are known 

 numerous asporogenous strains, hereditarily fixed. 



The starting point of the second series, which leads to the diploid 

 character of sprout mycelium, is formed by Zygosaccharomyces and its 

 relatives. In this form, as in Schizosaccharomyces octosporus, the asco- 

 spores, immediately after their liberation from the ascus, may copulate 

 with one another or with vegetative cells or they may change partheno- 

 genetically to new asci. This has been observed only as an exception in 

 Zygosaccharomyces Chevalieri, but is the rule in the following groups: the 

 west African Saccharomyces Chevalieri, S. Mangini, in Willia Saturnus, on 

 earth in the Himalayas and in the yeast Johannisberg II (Guillermond, 

 1910, 1914). At germination the spores swell and rupture the ascus wall. 



AM 



m 



m 



•piQ. 96. — Yeast Johannisberg II. Copulation and developnent of asci. (X750; after 



Guillermond, 1905.) 



Some of them grow normally to a sprout mycelium. Some, before, dur- 

 ing or after the rupture of the ascus wall, copulate in pairs (Fig. 96, 1 to 6). 

 In contrast to Zygosaccharomyces Chevalieri, the zygote does not change 

 into an ascus but sprout cells, which develop to an apparently diploid 

 sprout mycelium, appear in the copulation canals, occasionally also on 

 the whole upper surface of the copulating cells (Fig. 96, 7 to 9). Later, 

 without further sexual processes, as in S. cerevisiae, the ascospores arise 

 in the vegetative cells. 



The end of this second series is formed by Saccharomy codes Ludwigii 

 in slime flux of oak (Guillermond, 1903, 1905). Its asci almost always 

 contain four spores which lie in pairs at the two poles (Fig. 97, 1 and 2). 

 The spores at one pole result from the division of one nucleus; thus they 

 are sister cells and remain connected by a protoplasmic layer remaining 

 from the periplasm. At germination they swell much in the ascus and 

 form small beaks toward each other which broaden to copulation canals 

 (Fig. 97, 1 to 4). At times several spores fuse. Two cells of the same 



