374 MICRO-ORGANISMS AND FERMENTATION. 



Zygosaccharomycetes appear to occur fairly frequently in 

 nature. Since Barker drew attention to this peculiar genus 

 of Saccharomycetes, similar species have been found by other 

 workers. Thus, for instance, Holm has found them on figs 

 and pears, in dunder, and in Barbados sugar. 



Saccharo my codes Ludwigii or Saccharomyces Ludwigii 

 Hansen. (Figs. 55, 56, and 82.) 



This remarkable 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- 

 taken from Hansen's investigations. The cells are very 

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

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

 cell-combinations. The vegetative growths in wort-gelatine 

 are round like those of the majority of the Saccharomycetes, 

 and are either pale grey, or faintly yellow. In wort, it yields- 

 only 1-2 per cent, by volume of alcohol, even after a long- 

 continued fermentation ; and this accords with the fact that 

 maltose is not fermented by this species. In dextrose solutions, 

 on the other hand, it yields up to 10 per cent, by volume of 

 alcohol. It inverts saccharose, but does not ferment solutions 

 of lactose and dextrin, neither does it saccharify starch paste. 

 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. 



It is characteristic of this species that a fusion of germinated 

 spores often occurs, especially in the case of young spores r 

 and these new formations develop germ-filaments (pro- 

 mycelium), from which new yeast cells are gradually marked off 

 by sharp transverse septa (Figs. 55, 56). At the ends of 

 these cells, buds develop, and these again are marked off by 

 transverse septa. 



According to Hansen, a stable asporogenous variety cannot 

 be prepared by cultivation at temperatures lying between the 

 maximum for spore-formation and the maximum for budding. 

 On the other hand, Hansen found that a number of cells lost 



