HEMIASCOMYCETES 149 



tures, long filaments. As far as is known, in all these cell multiplications 

 nuclear divisions are amitotic (Fig. 95, 1 to 4). 



Under certain conditions of nourishment, especially in age, with the 

 exhaustion of nutrient, or on solid substrates like gypsum blocks, asci 

 with ascospores appear in the cultures, as in the Endomycetaceae. This 

 character distinguishes the family from numerous other families dis- 

 cussed in this book, belonging to other groups which also may form a 

 sprout mycelium, and especially also from the imperfect yeasts, as 

 Torula, Mycoderma, il Dematium," Cryptococcus and Monilia. 



In the wild yeasts, the number of ascospores varies from one to twelve ; 

 in many industrial yeasts, certain numbers predominate, thus in Schizo- 

 saccharomyces octosporus 4 or 8, in Saccharomyces cerevisiae and the yeast 

 Johannisberg II 4 and in Saccharomyces Pastorianus 2. They are very 

 resistant and, in the wine yeasts, may winter over in the soil of the vine- 

 yard. Generally they are spherical or oval; in Willia anomala, as in 

 Ascoidea and Endomyces fibuliger, they are hemispherical, with the flat 

 wall projecting over the edge like a hat brim. In Willia Saturnus they 

 are citriform and (like Endomyces capsularis) provided with an equatorial 

 projecting ring; in Pichia membranifaciens, they are irregular, spherical, 

 hemispherical to tetrahedral; in Nematospora, they are fusiform and pro- 

 vided with a slender appendage at each end. They are generally smooth, 

 but rough in Debaryomyces and Nadsonia. In contrast to the majority 

 of the Endomycetaceae, the wall is usually one layered; in rarer cases, 

 two layered, as in the Endomycetaceae, in which case the outer layer 

 ruptures on germination. 



The processes in the formation of ascospores may be next discussed 

 in connection with Schizosaccharomyces octosporus, on figs and grapes 

 in the Mediterranean region (Guillermond, 1903, 1905, 1910, 1917; 

 Coker and Wilson, 191 1). About three days after the culture is made the 

 cells copulate in pairs by short tubes (Fig. 92, 1 to 6). In cell chains, it 

 occasionally happens that the separating wall between two sister cells 

 is dissolved (adelphogamy). Two nuclei migrate into the copulation 

 canal and fuse; the copulation canal broadens and the two individuals 

 develop into a barrel-shaped structure in which, within approximately a 

 half-hour, after three or more, rarely two, nuclear divisions, eight — rarely 

 four — spores appear (Fig. 92, 7 to 22). Often the copulation canal does 

 not attain the breadth of the mother cell, and the young ascus is shaped 

 like a dumbbell between whose ends the eight spores are divided. At 

 germination the spores in the ascus swell, the ascus wall ruptures, the 

 spores are freed, and each is divided by a septum into two daughter cells 

 which later divide in a similar manner. 



Under unfavorable conditions, copulation may occur earlier, so that 

 already in the ascus the ascospores copulate with spores of the same or 

 neighboring ascus. Other cultures have a tendency to become aspor- 



