302 INTRODUCTION TO THE STUDY OF FUNGI 



become larger ; the greater part of the latter form spores in 

 their inner space through the free formation of cells, like those 

 of an ascus, and then becoming thicker at the cost of the 

 protoplasm, at last entirely fill the membrane of the utricle. 

 We can produce the same phenomenon if we thoroughly wash 

 fresh yeast, and, mixing a little clear water with it, let it stand. 

 The formation of the spores here follows, by a sufficient supply 

 of water, at the cost of the organic substance, which has 

 assimilated during the fermentation ; we must seek it in the 

 yeast which is used technically when, after its fermentation is 

 complete, it is laid aside clear and wet. The spores begin, 

 when they are brought into a suitable liquid, to sprout like 

 the vegetating cells, in order to produce new repeated genera- 

 tions of the latter. No other forms of development are known 

 for the Fungus which is found in yeast." x 



The yeast Fungus is the principal promoter of the 

 alcoholic fermentation which appears in practical life, especi- 

 ally the greater part of beer and spirit fermentation. That 

 which is distinguished by the name of harm, and the yeast 

 deposited at the bottom of the cask, are in many cases — not in 

 all — the same Fungi, which in a lower temperature remains at 

 the bottom, and collects as under-yeast ; by higher temperature 

 it accumulates in the froth on the surface of the fluid, and is 

 called barm. There is a slight difference in the form of the 

 yeasts, but the one form can be transferred to the other, by 

 changing the temperature of the fermentation. Further 

 details will have to be sought in some work dealing specially 

 with the subject, as we are only interested in furnishing an 

 outline of the organisms concerned in the processes of putre- 

 faction and fermentation. 



BIBLIOGRAPHY 



Sacoakdo, P. A. " Saccharomycetaceae," by J. B. de Toni, and "Scbizomy- 



cetaceae," by De Toni et V. Trevisan, in Sylloge Fungorum, vol. viii. Padua, 



1889. 

 Tkotjessaet, E. L. Microbes, Ferments, and Moulds. Cuts. Sm. 8vo. London, 



1889. 

 Grove, AV. B. A Synopsis of Bacteria, and Yeast Fungi. Sm. [8vo. Cuts. 



London, 1884. 



1 De Bary On Mildew and Fermentation, Berlin (1872), p. 61. 



