198 FAMILY OF SACCHAROMYCETACEAE 



velopment. Speculation seems to be rapid and appears at the end of 

 two or three days on solid media (slices of carrot, beer wort or wine 

 to which gelatin has been added). It may happen that, at the end 

 of fermentation, the vegetative cells in the sediment may contain 

 ascospores but, in this case, sporulation is feeble. The ascs form 

 with difficulty on plaster of Paris blocks; according to Seiter they 

 appear at the end of six or seven hours at 25 C. 



Sporulation is preceded by a sexual phenomenon which was 

 studied by Guilliermond l in 1901. The asc results from an isogamic 

 copulation which takes place between two neighboring cells. These 

 unite by means of a copulation canal through which the contents of 



the two cells mix. The fusion results in the 

 formation of a large oval zygospore (6-10.5 

 wide and 14-20.5 long). This transforms 

 slowly into an asc. Sometimes the fusion 

 remains incomplete, and the asc seems to be 

 formed of two enlarged parts united by a 

 canal. All intermediary stages are found, 

 however, between complete and incomplete 

 fusion (Figs. 14, 15, and 16). 



The ascospores, always 4 or 8 in each 

 asc, are usually ellipsoidal in shape. They 

 FigTT^T-Karyokenesism are surrounded by a membrane, covered 

 the Ascs of Schizosac- with a starchy reserve material which stains 

 charomycesOctosporus. blue with io( J ine (Lindner); this is utilized 



during germination. The wall of the asc persists, or more often disap- 

 pears immediately, before germination; the ascospores, having been set 

 free, separate or remain attached. Germination begins by a. swelling 

 of the ascospores which take the appearance of vegetative cells and 

 divide in the usual manner. On nutrient gelatin the colonies are round 

 with a thick center. 



We have seen that Beijerinck noticed, when the yeast was inoc- 

 ulated onto gelatin, that three sorts of colonies were obtainable; first, 

 white colonies made up of cells which formed ascospores; secondly, 

 clear brown colonies made up of only vegetative cells; thirdly, light 

 brown colonies made up of cells forming ascs and those with no ascs. 



1 Guilliermond, A. Recherches histologique sur la sporulation des Schizo- 

 saccharomycetes. Comp. Rend. Acad. Sciences, 133, 1901 ; Recherches cytologiques 

 sur les levures et quelques moisissures a form levures. These for the Doctorate 

 in Sciences at the Sorbonne, Storck, Lyon, 1902. Summarized in the Revue 

 generale de Botanique, 15, 1903; Recherches sur le developpement du Gloeosporium 

 nervisequum et sa pretendue transformation en levures. Rev. gen. de Bot. 20, 

 1909. 



