214 FAMILY OF SACCHAROMYCETACEAE 



The two gametes unite by a copulation canal formed by the union 

 of two small projections sent out from each cell. During this phenom- 

 enon the small cell remains adherent to the mother cell and after 

 the development of the copulation canal may detach from this cell. 

 The contents of the male gamete emigrate to the female gamete, 

 both protoplasms fuse, and the female gamete is transformed into an 

 egg; this changes very quickly into an asc, and each asc contains 

 usually from one to two ascospores; exceptionally one may find 

 three, or even four. 



Besides this heterogamic conjugation which has been described, 

 frequently one may observe a series of transitional forms between the 

 iso- and heterogamic. The conjugation presents the same characteris- 

 tics in cultures on carrot and beer wort. However, in the latter me- 

 dium the yeast seems to take on the elongated form. 



The minimum temperature for sporulation on Gorodkowa's agar 

 seems to be situated around 5. At this temperature the first rudi- 

 ments of ascospores appear at the end of two weeks; at from 13-15 

 the ascospores form at the end of eight days; from 19-20 they 

 appear at the end of 56 hours; the optimum temperature seems to 

 rest between 23 and 30, while the maximum temperature is situated 

 somewhere between 30 and 32. The ascospores remain enclosed in 

 the wall of the asc. During the first stages in germination, the wall 

 is ruptured, and the ascospores germinate by ordinary budding. 



In plate cultures the colony is of yellowish white with a peripheral 

 zone made up of canals; the center is a little elevated and is con- 

 structed of rather thick, irregular folds. In streak cultures the colony 

 presents the same characteristics. In stab cultures the yeast develops 

 abundantly along the line of inoculation and forms a large number 

 of small colonies. The colonies enlarge toward the surface. The 

 giant colonies on must gelatin at from 15-20 have a dry appearance 

 and are only a few millimeters in diameter. The color is yellowish 

 white, the center is slightly raised, 



This yeast inverts saccharose when cultivated in must. It forms 

 carbon dioxide which gives evidence of fermentation. This fermen- 

 tation is well demonstrated by Lindner's droplet culture method. 

 According to this method the yeast ferments dextrose and levulose. 

 It has no action on lactose, d-galactose, maltose, dextrin and raffinose. 



The existence of a heterogamic conjugation is of special biological 

 interest, because heterogamy up to the present time, has been rarely 

 observed among yeasts. Guilliermond found it in the yeasts which 

 he named Saccharomyces chevalieri. In this same paper Guilliermond 

 has given a rather extended discussion on this subject in its relations 

 to the yeasts. 



