ALCOHOLIC FERMENTS. 159 



As in most vegetable cells, a cell-nucleus (first discovered 

 by Schmitz) is also found in the yeast cell, and its presence 

 can be proved by staining with osmic acid or with picric acid 

 and hcematoxylin. According to Hansen this cell-nucleus is 

 either spherical or disc-shaped. In old film-formations of 

 Saccharomycetes, he found cells which distinctly showed the 

 nucleus without any treatment. Janssens observed the 

 partition of the cell-nucleus both in the budding and in the 

 spore-formation of the Saccharomycetes. 



CLASSIFICATION OF THE GENUS SACCHAROMYCES. 



"BUDDING FUNGI, mostly without a mycelium, the indivi- 

 dual species of which occur with cells of different form and 

 size. Under certain treatment, and sometimes also ^vithout 

 any previous treatment, cell-nuclei are seen. Under certain 

 conditions the cells develop ENDOGENOUS SPORES ; the germi- 

 nating spores of most species grow to budding cells; in 

 exceptional cases a promycelium is first formed. Number 

 of spores 1 to 10, most frequently 1 to 4. Under favourable 

 conditions the cells secrete a gelatinous network, in ^vhich 

 they lie imbedded. 



The greater number of the species induce alcoholic fer- 

 mentation. 



SACCHAROMYCES CEREVISLE I. 

 (Figs. 3436.) 



This and the five following species (Sacch. Pastorianus 

 I., II., and III., Sacch. ellipsoideus I. and 77.), all develop 

 invertase ; with this they effect the hydrolysis of saccharose 

 to invert-sugar, and they ferment the latter. They produce 

 a vigorous fermentation in dextrose solutions, and likewise in 

 maltose solutions, especially when a nutrient liquid such as 

 yeast-water is added. All are vigorous alcoholic ferments 



1 This top-fermentation yeast must not be confused with Uansen's 

 Carlsberg bottom-yeast No. I. 



