440 SACCHAROMYCES APICULATUS. 



its injurious influence on the wine yeast diminished. This is 

 clearly evident from the chart. The influence of Apiculatus on 

 the weaker red wine, Karthaus yeast is still more adverse than 

 with the Steinberg yeast, and is more clearly evident from the 

 chart. On the 2oth day the amount of carbon dioxide liberated 

 was 39.6 grms. with the Karthaus yeast alone, 9.4 grms. with 

 Apicidatus, and 10.8 grms. with the two together, so that the 

 wine yeast had hardly come into action at all by that time. 

 However, as soon as the proportion of alcohol reached i per cent. 

 by weight, the fermentation increased rapidly, more especially 

 from the 4oth day, when the alcohol content had attained about 

 2 per cent., the wine yeast being then able to free itself from the 

 Apiculatus enfeebled by the alcohol. 



The cause of the restrictive influence of the Apiculatus yeasts 

 on the fermentative activity of wine yeasts has not yet been de- 

 finitely ascertained. MULLER-THURGAU (XXX. and XYI.) has 

 shown that when Apiculatus acts in conjunction with wine yeast 

 in fruit must or grape must, smaller quantities of yeast are 

 formed than when the latter is acting alone. It is, however, 

 probable that the former restricts the fermentative activity of 

 the individual cells, as well as their growth, either by lowering 

 their fermentative energy or shortening their period of activity, 

 or both. 



The active agent in restricting the other yeasts probably con- 

 sists chiefly of volatile acids. True, as MULLER-THURGAU (XXX.) 

 asserts, the quantity of these acids is smaller than would corre- 

 spond to their powerful adverse influence, at least if they con- 

 sisted entirely of acetic acid but the more powerful formic acid 

 is also present, and probably other substances capable of retard- 

 ing growth and fermentation. When the fermentative action of 

 Sacch. apiculatus is restricted by the liberated alcohol, the further 

 production of these injurious substances ceases ; and at the same 

 time the progress of fermentation indicates that the injurious 

 substances already present are either destroyed or converted into 

 others of less power (e.g., the volatile acids into esters). 



Experiments prove that the more vigorous the elliptical yeast 

 the less is it affected by Apiculatus yeast, on the one hand because 

 of its greater power of resisting injurious influences, and also 

 because it produces more rapidly the requisite quantity of alcohol 

 for checking the enemy On this account the difficult period of 

 the struggle will be traversed more quickly when the proportion 

 of Sacch. ellipsoideus to Sacch. apiculatus is greater in the sow- 

 ing. In fact, experiments performed on this point by ROHLING 

 (I.) showed that when a large proportion of elliptical yeast is 

 sown along with a small quantity of Apiculatus yeast, the latter 

 is kept in the background and fermentation is scarcely hindered 

 at all, though retardation occurs when even a small extra 

 additional quantity of volatile acid is formed. The best flavoured 



