STUDIES ON FERMENTATION. 157 



the must fermenting after the submersion of the cellular plants. 

 It follows that the cells, or groups of cells, of a dark colour 

 which cover the grapes, or the woody part of the clusters, are 

 actual germs of the cells of yeast ; more correctly speaking, that 

 germs of yeast-cells exist amongst these groups, for it would not 

 be consistent with truth to say that the various germinating 

 forms present in the dust on the surface of grapes must all 

 of them give rise to actual corresponding ferments. Thus the 

 flask-shaped spores c, c, ... in Plate VIII., are reproductive 

 organs of alternaria tenuis, which have probably nothing 

 in common with alcoholic ferment or ferments, properly so 

 called, except their outward form. "VVe may repeat, however, 

 and it is a point of great importance to bear in mind, that the 

 cells of yeast originate from some or other of the little, brownish, 

 organized bodies, which the microscope reveals in such numbers 

 amongst the particles of dust existing on the surface of fruits. 



The impossibility, which we have already demonstrated 

 (Chapter III., § 3), of making grape juice ferment apart from 

 the action of external particles of dust, and the knowledge 

 which we have just acquired, that the particles of dust on the 

 surface of the grapes and woody peduncles, at the moment when 

 the grapes have attained maturity, contain certain reproductive 

 cells which give rise to certain ferments, naturally lead us to the 

 investigation of another point, which concerns the period at 

 which these germs make their appearance on the difierent parts 

 of the vine plant. The two following experiments tend to prove 

 that the ferment can only appear about the time when the 

 grapes attain maturity, and that it disappears during the winter, 

 not to reappear before the end of the following summer. 



I. In the month of October, 1873, we procured from a vine- 

 yard in the canton of Arbois some of the woody parts of very 

 ripe clusters of grapes, taking the precaution to cut off all the 

 grapes, one by one, with a very clean pair of scissors, whilst 

 still on the vine ; we then wrapped up the woody parts of the 

 clusters, thus deprived of their grapes, in thin paper, to convey 

 .them to Paris. Our only object at that time was to secure for 



