ALCOHOLIC FERMENTS. 151 



in must absolutely pure cultures of which were prepared by 

 Hanserfs method were investigated by Marx, both from a 

 botanical point of view and with reference to their chemical 

 action on the nutritive liquid. The time required for spore- 

 formation was very different for the different species, and 

 likewise the number of spore-forming cells and the number 

 of spores in individual cells exhibited striking and constant 

 differences. In connection with this, it is especially of 

 interest that the pure cultivated species show distinct 

 differences in fermentative power and in the production of 

 volatile substances, which impart a special bouquet to wine, 

 and finally in their power of resistance to different acids 

 and to elevated temperatures. As marked differences in 

 taste are produced by not a few species, Marx is justified 

 in emphasising the practical importance of such investiga- 

 tions, since it thus becomes possible, by the addition of 

 yeasts of known properties to wine-must, to produce wines 

 having definite characters as regards taste, &c., independent 

 of the locality. 



More recently Amthor has also investigated a number of 

 absolutely pure cultures of wine yeasts, and has detected 

 typical differences both with regard to spore-formation and 

 to the time of duration of the fermentation, finally also in 

 the chemical composition of the wines produced. Similar 

 results have also been obtained by Jacquemin, Rommier, 

 Martinand, and Rietsch, in France ; Muller-Thurgau, in 

 Switzerland ; Nathan and Wortmann, in Germany ; Mack 

 and Portele, in Austria ; Forti and Pichi, in Italy ; the com- 

 parative experiments conducted by these authors having 

 been partly carried out on a large practical scale. 



(g) Variations in the species of the Saccharomycetes. 

 Hansens numerous investigations have proved that the Sac- 

 charomycetes are affected in various ways by external in- 

 fluences. From the results recorded in the previous sections, 

 we are perfectly justified in saying that there are a number of 

 species, not only of the so-called wild yeasts (species which 



