FORMS OF CELLS 



Hansen). 



(after 



different forms, depending upon the medium in which they are culti- 

 vated and their age. It is thus, for example, in old cultures that the 

 wider cells diminish generally at the expense of the longer ones. The 

 different species of yeasts have somewhat the same 

 shape and are distinguished with some difficulty from 

 one another. If S. cerevisiae is compared with S. 

 Pastorianus or S. ellipsoideus, quite noticeable differ- 

 ences are apparent. While S. cerevisiae usually pre- 

 sents round cells and S. ellipsoideus egg-shaped cells, 

 S. Pastorianus presents, to the contrary, elongated 

 cells, often in the shape of a sausage. But besides 

 these elongated forms, one may find in cultures round 

 cells which may scarcely be differentiated from S. 

 cerevisiae or S. ellipsoideus. On the other hand, in 

 culture of S. cerevisiae and S. ellipsoideus may be found round cells, 

 and also elliptical cells which bear much resemblance to S. Pastorianus. 

 It is thus apparent that these three species may 

 not be closely differentiated by the shape of the 

 cells. There is always a predominating form 

 which attracts attention; with S. cerevisiae the 

 predominating form is round ; with S. ellipsoideus 

 it is elliptical, while with S. Pastorianus it is 

 most frequently elongated. 



The majority of the yeasts, notably those of 



fastorianus (accord- industrial importance (beer, alcohol, wine and 

 ing to Hansen). . , N . . . . . . , 



cider), present a mixture of spherical and elon- 



gated cells. Although this is the case, a predominating form exists 

 which may be of three types, the cerevisiae type, the ellipsoideus 

 type or the Pastorianus type. 



Among the yeasts, which are very numerous and in which the cell 

 shapes are variable and in- 

 definite, are often found 

 certain species, or groups 

 of species, in which the cells 

 present a characteristic 

 shape and which are sepa- . 

 rated closely from the pre- 

 ceding yeasts. Hansenia 

 apiculata, for example, of- 

 fers cells which are usually 

 of the shape of a lemon, being provided with small projections from 

 which the name apiculata is derived. A series of species of yeasts is 

 known which possesses a similar shape and these, without doubt, are 

 varieties of Hansenia apiculata or neighboring species. (See Fig. 4, g.) 



4. Showing the Different Shapes of 

 Yeast Cells. 



a, cerevisiae type; b, ellipsoideus; c 1 , c 2 , Pastorianus type; 

 d, Mycoderma type; e, f, Torula type; g, apiculate 

 type; h, Saccharomycodes type; i, Schizosaccharomyces; 

 i 1 , & 2 , Mycelial structures; I, m 1 , m 2 , m 3 , Amoeboid forma 

 (according to Lindner). 



