SPORULATION 13 



durable cells (Dauernzellen) ; he regards them as resistant organs 

 which serve to perpetuate the species over unfavorable periods. In 

 this, they are similar to the ascospores. Perhaps they may be 

 regarded in the same light as cysts, or clamydospores, which have 

 been observed so frequently in the Endomyces. 



When these durable cells are placed again in favorable circum- 

 stances, their membrane is broken and budding takes place giving 

 rise to spherical and elongated yeasts, be they separated or in groups. 



Sporulation 



Sporulation is a form of resistance which allows the yeast to 

 remain viable, even though active budding has stopped. It plays 

 an important role in the hibernation of yeasts, permitting them to 

 pass the winter in the ground of vineyards where they are deposited 

 in the autumn. Sporulation is observed in old cultures where food 

 is scarce, also in certain solid media such as carrots or gelatin which 

 are not very favorable for budding. It is especially easy to secure 

 Sporulation by. submitting the yeasts to starvation after they have 

 been able to build up sufficient reserve products necessary for the 

 formation of ascospores. 



We shall take up in a following chapter the details which determine 

 Sporulation; therefore this question will not receive attention at 

 this time. 



Internal, or ascospores, were observed for the first time by Schwann 

 in 1839 and described by Seynes. They were regarded by some 

 authors, notabty Van Tieghm, as resulting from a sort of encystment 

 resulting from some pathological process. Brefeld considered these 

 cells, which bear spores, as sporangia or cysts. On the contrary, 

 Rees, 1 de Bary, 2 and later Hansen, 3 likened the sporangia of yeasts 

 to the asc of the Ascomycetes and regarded the yeasts as a group of 

 fungi. This opinion has been entirely confirmed by our investiga- 

 tions on the cytological phenomena of the formation of ascospores, 

 and especially by the discovery in certain yeasts of a copulation 

 in the origin of the asc. It is definitely admitted today. 



Sporulation is indicated by any cell, either yeast cell or a cell 

 constituting a rudimentary mycelium. In this way certain yeasts 

 (S. Ludwigii, Pichia membranaefaciens) are able to form ascospores 

 in mycelial cells developing on the surface of old cultures. Each 

 cell, then, seems able to develop into an asc. 



1 Rees, H. 1870. Botan. Untersuchungen uber die Alcoholgarungspilze, Leipzig. 



2 De Bary, A. Morphologic des Pilzes. Leipzig, 1866. 



3 Hansen, E. C. Recherches sur la physiologie et la morphologic des ferments 

 alcooliques. Comp. Rend, des trav. du lab. de Carlsberg, 2, 1883. 



