6o6 



laginous substances frequently lead to the separation in insoluble 

 form of various pectinous compounds. The variety of yeast used, 

 plays at the most but a secondary part in determining the rate of 

 fermentation and from the results obtained in experiments made 

 with yeasts of limited fermentative power, it seems probable that 

 normally the rate is not far short of the maximum, which the com- 

 position of the. juice as regards assimilable nitrogenous matter 

 allows. 



The more rapid fermentation of the " keeved " juice is due 

 to the greater exposure to air, the aeration of the juice having a 

 marked effect upon the rate of fermentation. The temperature at 

 which the fermentations are conducted affects the rate in the 

 customary manner. 



E. B. PEARCE and B. T. P. BARKER. The Yeast Flora of Bottled 

 Ciders. Journ. of Agricultural Science, Vol. Ill, Part I. De- 

 cember 1908. 



The work described in this paper deals exclusively with the 

 yeast flora of certain hottled ciders. It was undertaken as a section 

 of an extensive scheme of investigation of the organisms which are 

 concerned in the fermentation of English-made ciders. Apart from 

 the more purely biological side of the question the main objects 

 of the whole scheme are to determine how far the customary method 

 of conducting the fermentation of cider in this country is satisfac- 

 tory, and whether it could be improved from a practical point of 

 view, by certain modifications or by the substitution of other pro- 

 cesses, such, for example, as the use of selected yeasts. Ferment- 

 ation with pure cultures of special yeasts has been adopted with 

 great success in the brewing industry ; it has also been applied with 

 some success to the preparation of wines, while its use in connexion 

 with cider has not been so exhaustively tested. The method used 

 to isolate in the pure state the different varieties of yeasts present 

 in the ciders under investigation was that of fractional plate cul- 

 tures on 10 / beer-wort gelatine. The results obtained in the 

 culture of the yeasts upon different media were used both from 

 the point of view of ascertaining the specific characters of each 

 form, and also of distinguishing the varieties from one another. 



Detailed description is given of the species isolated. The five 

 samples examined had a flora so diverse, that it is clear that the 

 fermentation of cider in the ordinary manner is most uncertain in 



