GERMINATION OF ASCOSPORES 35 



asc, but very often the wall of the asc is absorbed and the spores are 

 set free. 



In the latter case, they may isolate themselves or remain united. 

 At the time of germination, they commence to enlarge and become 

 large cells similar to those in the vegetative stage. During this time 

 the wall of the asc, if it exists up to A 



this time, breaks up and is absorbed. QJY} ( \^prr) (L^ CQC~C/ 

 But it often remains in the state of a U 



veil during the partition of the asco- Chv--^> 

 spores. The ascospores sometimes re- \r^ 

 main spherical and form in the middle 

 a wall which divides them into two 

 daughter cells. These become round Fig> 43. - Germination of Asco- 

 and separate. But more often they spores in Schizosaccharomyces 

 elongate. (Fig. 14, a.) 



In Sch. mellacei and Sch. Pombe the ascospores germinate after 

 the absorption of the membrane of the asc. This absorption is 

 accomplished very quickly. They enlarge and each gives rise to a 

 little tube which soon divides and forms two bacilli-like cells. Soon 

 these, in their turn, divide in the same manner 

 and furnish numerous generations of vegetative 

 cells. 



Direct Germination of Ascospores in Asc: 

 The investigations of Hansen and Guilliermond 

 have shown that under certain conditions bud- 

 ding may be suppressed and that the asco- 

 spores, after becoming enlarged, are susceptible 

 Fig. 44. Abnormal Ger- ' . ' >. .^ 



mination of Ascospores to germination without undergoing multiphca- 

 in Saccharomyces Lud- ^ on ^^{ s produces, then, a curious shortening 



wzgii, on slices of carrot. , 



ot the development. 



The zygospore resulting from 



the fusion of two ascosporea Hansen 1 has observed this phenomenon in 



changes directly into an asc. x 



Saccharomyces cerevisiae and the yeast Johan- 



nisberg II in the following manner. He placed some ascs of this 

 yeast in beer wort in a Freudenreich flask. At the end of two hours, 

 the ascospores enlarged and often copulated. After from three to five 

 hours, the wall of the asc broke and the ascospores grew larger and 

 larger. He placed some others in Freudenreich flasks containing a 

 saturated solution of calcium sulfate. (It will be seen further on 

 that calcium sulfate has the property of arresting immediate budding.) 

 Under these conditions the ascospores are not able to germinate by 

 budding and immediately go into ascs. 



1 Hansen, E. C. Recherches sur la physiologic et la morphologic des ferments 

 alcooliques. Comp. Rend, des trav. lab. de Carlsberg, 5, 1902. 



