32 MORPHOLOGY AND DEVELOPMENT OF YEASTS 



remain attached to one another, making a chain. With rare excep- 

 tions, the copulation canal of the zygospore germinates always in 

 the same way. The simultaneous production of many buds is not 

 observed at many points on the surface as with the yeast Johannis- 

 berg II. 



About four ascospores germinate alone without preliminary 

 copulation. In this case, after swelling, they form a new germinating 

 tube in which the end is enlarged and take the form of an ordinary 

 vegetative cell. Here again germination takes place only in a single 

 direction and the ascospore forms only a single germinating tube at 

 a time. 



The germination of old ascospores is accomplished in a different 

 manner. Hansen has observed that old ascospores, whether due to 

 humidity or dryness, lose their tendency to fuse and germinate alone. 

 They develop, then, in a peculiar manner. Each forms a germinat- 

 ing tube which, in developing, produces a long filamentous form of 

 very many cells superimposed and capable of ramifying. It presents 

 something the appearance of a mycelium. Hansen has given the 

 name promycelium to this formation and compared it to the filaments 

 which result from the germination of chlamydospores of the Ustila- 

 ginales. Guilliermond has verified this observation in the germina- 

 tion of ascospores from old cultures and his observations have allowed 

 an explanation of this structure, improperly called a promycelium. 

 As has been said in the preceding paragraph, the ascospores from 

 very old cultures find themselves obstructed in copulation. A great 

 number are dead, and the cells which survive are often isolated and 

 surrounded by spores which are incapable of developing. On account 

 of this they may have to search other ascs with which to unite. 

 They send out long tubes more or less branched which may accom- 

 plish a fusion but which more often do not unite. In this case the 

 tubes end up by walling off cells which dissociate and take the form 

 of vegetative cells. Under such conditions the greater part of the 

 ascospores find it necessary to germinate alone. One usually finds 

 a few which are able to copulate. 



Let us recall what we have described in S. Ludivigii, in which 

 the ascospores always germinate without preliminary copulation. 

 However, many of them preserve their traces of sexual attraction, 

 and send out, in germinating, long protuberances which do not accom- 

 plish anything. 



The germination of the ascospores of S. Ludwigii differs essen- 

 tially from the other yeasts, and in this one the ascospores, copulated 

 or not, do not produce many buds at various points on the surface, 

 but germinate in a single direction in which they form a sort of 



