152 COMPARATIVE MORPHOLOGY OF FUNGI 



into a fusion cell and there forms a spore (Fig. 93, 6 to 11); it may 

 just as often occur, however, between a still sprouting mother cell and a 

 young daughter cell (Fig. 93, 12 to 14) where the content of a daughter 

 cell migrates back into a mother cell (Guillermond, 1912a). 



This pedogamous form of the copulation becomes the normal in 

 the following species. The West African Zygosaccharomyces Chevalieri 

 and the west European Z. Pastori and Z. Nadsonii, in the Russian 

 Debaryomyces tyrocola, in the French D. Kloeckeri and in the Russian 

 Nadsonia fulvescens and N. elongata (Nadson and Konokotina, 1911, 

 Konokotina, 1913; Guillermond, 1918, 1919, 1920; Guillermond 

 and Peju, 1919, 1920 and 1921). Exceptionally there is no difference 

 between the fusion cells, and the daughter cells have already developed 

 to the size of the mother cell (Fig. 93, 15 and 16). In most cases, copu- 

 lation takes place (in case it is still necessary and is successful) between a 

 mother cell and a daughter cell which has just been formed (Fig. 93, 

 17 to 23); generally the content of smaller cells returns to that of the 

 larger, which is abjointed and develops to a 1 to 4 spored ascus, while 

 the smaller fusion cell disappears. Besides, especially in Zygosaccharo- 

 myces Chevalieri, with insufficient nourishment the two ascospores may 

 copulate after they have swollen and ruptured the ascus wall or an asco- 

 spore may copulate with a sprout cell and change into a one-spored 

 ascus, or the ascospore, without any copulation, may function as an ascus 

 and form ascospores within. 



In Nadsonia (Guilliermondia) , spore formation does not generally 

 occur inside the larger fusion cell; on the side opposite the copulation 

 canal, a sprout cell receives the united contents of both fusion cells 

 and changes into 1 to 2 brown-walled spores. It is still obscure whether 

 this relationship has a deeper significance and whether one may ascribe 

 to it in principle the same significance as to the development of the 

 ascogenous hypha of the typical Ascomycetes. 



From this paedogamous group, the lines diverge to entire partheno- 

 genesis and to diploid sprout mycelium. 



The starting point of the first series is Zygosaccharomyces Pastorii and 

 its relatives. In this group, as earlier in Debaryomyces globosus, although 

 many cells form copulation processes, only a few are able to copulate 

 because of increasing weakening of sexuality. This character continues 

 in Torulaspora Delbrueckii, in English beer, and in T. Rosei, in slime flux 

 of oak. On favorable media the sprout cells form numerous copulation 

 tubes and seem to attempt to anastomose with each other. (Fig. 94, 1 to 

 3). Often they lie so close that the pressure of the cover glass no longer 

 suffices to isolate them. Exceptionally, the cell content migrates to the 

 copulation bridge and there, after a sexual act, the ascospores arise. 

 Generally the separating wall is no longer dissolved, but each cell forms 

 1 to 4 spores parthenogenetically (Guillermond, 1912a). 



