CHAPTER IX 

 CLASSIFICATION OF THE YEASTS 



WE have seen, in the preceding chapters, that the yeasts may 

 be regarded as making up a group of lower Ascomycetes 

 closely related to the family of Endomyces. It has been 

 shown, also, that they seem to be derived from an ancestral form re- 

 lated to Eremascus fertilis which may give birth at times to various 

 representatives of Endomycetes and yeasts. On account of the close 

 relations which exist between the yeasts and Endomycetes, Van 

 Tieghem, 1 in his recent classification, has attempted to place them 

 in one group, the Eremascines. Hansen, on the contrary, considers 

 the yeasts as making up a special family of Ascomycetes related to 

 Exoascus and Endomycetes which he calls Saccharomycetes. Although 

 among the Endomycetes and Saccharomycetes there exist all degrees 

 of transition, and although there are such varieties as End, javanensis, 

 which is with difficulty attached to either groups of these two families, 

 we believe with Schroter 2 that the yeasts should be made a distinct 

 family closely related to the Endomycetes and making up the group 

 Protoascines. The great number of the yeasts and their medical and 

 industrial significance seem to justify this opinion. How shall the 

 representatives of the Saccharomycetes be grouped? Profiting by the 

 morphological investigations of these later years by Hansen, 3 a clas- 

 sification may be proposed. This classification which was proposed 

 in 1904 and has been added to by the work of Klocker 4 and Lindner, 5 

 is today uniformly accepted. 



However the recent work on the systematic and phylogenic rela- 

 tions of the yeasts, not considering the great lines of this classifica- 

 tion, do not justify it completely. We shall adopt a classification a 

 little different from that of Hansen's. 



1 Van Tieghem. Elements de botanique. Masson et Cie., Paris, 4th Edition, 

 1906. 



2 Schroter, J. in Engler and PrantFs Die nat. Pflanzen. W. Englemann, Leipzig, 

 1889. 



3 Hansen, E. C. Grundlinien und Systematik der Saccharomyceten. Cent. 

 Bakt. 12 (1904), 528. 



4 Klocker, A. Deux nouveaux genres de la famille des Saccharomycetes. 

 Comp. Rend, des trav. du lab. de Carlsberg, 8, Book 4, 1909. 



5 Lindner, P. Mikroskopische Betriebskontrolle in den Garungswerben. Paul 

 Parey, Edit. Berlin, 6th edition, 1909. 



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