206 FAMILY OF SACCHAROMYCETACEAE 



Genus II. Zygosaccharomyces. Barker 



Ascs resulting from a copulation of two cells. Ascospores in a 

 membrane which is smooth. 



ZYGOSACCHAROMYCES BARKER!. (Barker) Saccardo-Sydow ' 



This species was found by Barker 2 in ginger beer to which had 

 been added saccharose and nutrient salts. They have the shapes of 

 small oval cells. (Fig. 82.) The maximum temperature for budding 



on nutrient gelatin is in the vicinity of 37- 

 38 C.; the minimum near 10-13 C. 



The ascospores appear easily, not only on 

 plaster blocks but in great numbers on other 

 media (nutrient gelatin, damp bread, potato, 

 carrot). The maximum temperature for 



the formation of ascospores on plaster blocks 

 Fig. 82. Zygosaccharomy- . . f 



ces Barkeri. Vegetative is 37-38 C., the minimum around 13 . At 



Barker)^ ASCS ^'^ 25 ~ 27 the first rudiments of ascospores 



appear at the end of 20 to 24 hours. 



The ascs result from an isogamic copulation between two cells. 

 This copulation, which has been described by Barker, is accomplished 

 in the same manner as in Sch. Pombe and mellacei. Two cells iden- 

 tical in characteristics, unite by means of a copulation canal formed by 

 the fusion of a little projection from each cell. The fusion remains 

 incomplete and the cells look like a dumb-bell. The ascospores are 

 formed in the swelled portions of the asc. Their number varies be- 

 tween two and four. (Fig. 82.) Zygosaccharomyces Barken does not 

 form a scum on sugar solutions, but at the end of 10 to 14 days a ring, 

 made up of oval cells, appears. It ferments dextrose, levulose, sac- 

 charose, and a-methylglucosides but neither maltose, lactose nor dextrine. 



ZYGOSACCHAROMYCES PRIORIANUS. Klocker 3 



This spscies, recovered by Klocker from the bodies of bees, pos- 

 sesses cells of varying shapes, elongated, round or oval, sometimes in the 

 shape of a sausage and almost always united. The temperature limits 

 of budding are: maximum, 36-38 C., and minimum, 38 C. 



Spores are easily produced on gelatin or wort, carrot or agar. 

 On plaster blocks, on the contrary, they form very slowly. The limits 

 for the formation of ascospores on plaster blocks saturated with beer 

 wort, are 27-28 and 3-9 C. 



1 Saccardo and Sydow. Syllage fungorum, Vol. II, 1902. 



2 Barker, P. A conjugating yeast (Zygosaccharomyces n. gen.). Proc. of 

 the Royal Society, Vol. 6, July 8, 1901. On the spore formation among the 

 Saccharomycetes. Journal of the Federate Institutes of Brewing, 8, 1902. 



3 Klocker. In Lafar's Handbuch der technischen Mykologie, Jena, 1904-1905. 



