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Such cases lead up to the conditions found in the large majority of 

 yeasts where ascospore formation takes place not only without effective 

 conjugation but without any vestiges of that process. 



Among forms with parthenogenetically produced asci Guilliermond 

 (1902) has observed a peculiar process in Saccharomy codes Ludwigii. Here 

 the rather elongated ascus gives rise to four ascospores; these on germination 

 swell up, put out beaks towards each other and fuse in pairs. Fusion is 

 usually between spores in the same ascus, but occasionally, when one of the 

 four ascospores has degenerated, between spores of different groups. Each 

 spore is uninucleate, the nuclei pass into the conjugating tube and there 

 fuse. A similar process takes place in Willia Satiirnns and in the so-called 

 Yeast of Johannesberg, II. 



Afterwards an outgrowth from the middle of the conjugation tube is 

 developed ; it may give rise to a short hypha which soon breaks up into 

 separate cells, it may produce lateral buds in an ordinary yeast-like manner, 

 or it may give rise at once, especially on carrot and under conditions favour- 

 able to ascus formation, to four endospores. In the last case the life-history 

 differs from that of Zygosaccharomyces principally in the abbreviation of the 

 vegetative phase, in other cases a vegetative phase is inserted not as usual 

 before conjugation, but between conjugation and the development of the 

 spores. Guilliermond regards the pairing of the ascospores as a secondary 

 process following the establishment of parthenogenesis. In any case it 

 admirably illustrates the plasticity of the simpler fungi. 



SACCHAROMYCETACEAE : BIBLIOGRAPHY 



1895 SCHIONNING, H. Nouvelle et singuliere formation de 1'ascus dans une levure. 



Meddelelser fra Carlsberg Laboratoriet. iv, p. 30. 



1901 BARKER, T. P. A Conjugating "Yeast." Proc. Roy. Soc. Ixviii, p. 345. 

 1901 GUILLIERMOND, A. Recherches sur la sporulation des Schizosaccharomycetes. 



Comptes Rendus Ac. Sci. cxxxiii, p. 242. 

 1901 HANSEN, E. C. Grundlinien zur Systematik der Saccharomyceten. Centralbl. fur 



Bakt. Abt. ii; xii, p. 529. 

 1903 GUILLIERMOND, A. Recherches sur la germination des spores chez le Schizosac- 



charomyces Ludwigii. Bull. Soc. Myc. de France, xix, p. 18. 

 1903 LEPESCHKIN, W. W. Zur Kenntniss der Erblichkeit bei den einzelligen Organismen. 



Centr. f. Bakt. Abt. ii; x, p. 145. 

 1905 GUILLIERMOND, A. Recherches sur la germination des spores et la conjugaison 



chez les levures. Rev. Gen. de Bot. xvii, p. 337. 



1909 KLOCKER, A. Deux nouveaux Genres de la Famille des Saccharomycetes. C. R. 

 des trav. du lab. de Carlsberg, vii, p. 273. 



1910 GUILLIERMOND, A. Sur un curieux exemple de parthe'noge'nese observe* dans une 

 levure. C. R. Soc. Biol. de Paris, Ixviii, p. 363. 



1910 GUILLIERMOND, A. Quelques remarques sur la copulation des levures. Ann. Myc. 

 vii, p. 287. 

 G.-V. 5 



