ALCOHOLIC FERMENTS. 179 



SACCHAROMYCES LUDWIGII. HANSEN. 

 (Figs. 29, 30.) 



This characteristic species, which was discovered by Ludwig 

 in the viscous secretion of the living oak, is the only one of 

 the known Saccharomycetes which can be recognised solely by 

 means of a microscopic examination. The following description 

 is from Hansen's investigations. The cells are very variable 

 in size, are elliptical, bottle-shaped, sausage- or frequently 

 lemon-shaped. Partition walls can occur in all the complex 

 cell-combinations. The vegetative growths in wort-gelatine 

 are like those of nearly all the Saccharomycetes round, 

 light grey, or faintly yellow. In wort it only yields 1'2 per 

 cent, (volume) of alcohol after a long continued fermenta- 

 tion ; and this is in accordance with the fact that maltose is 

 not fermented by this species. In dextrose solutions, on the 

 other hand, it yields alcohol up to 10 per cent, by volume. 

 It inverts saccharose, but does not ferment solutions of lactose 

 and dextrin, and it does not saccharify solutions of starch. 

 It readily develops spores in aqueous solutions of saccharose, 

 in wort-gelatine, in yeast-water, and in wort ; in the latter 

 case even when no film has formed. 



Spore-formation (Figs. 29, 30) occurs most rapidly at a 

 temperature of 25 C. It is characteristic of this species 

 that, especially in the case of the young spores, a fusion of 

 the germinated spores often occurs, and these new forma- 

 tions develop germ-filaments (promycelium), from which 

 new yeast-cells become gradually marked off by sharp trans- 

 verse septa. At the ends of these cells, buds are developed, 

 and these again become marked off by transverse septa. 



In old cultures there is often a strong tendency to form 

 mycelium, but portions are only exceptionally found the 

 cells of which are firmly united together, and which show 

 only slight constrictions ; these portions have distinct, 

 straight, transverse walls. Each cell of such colonies can 



