THE VINE-MILDEW. 267 



5. The disease of the cells does not induce putrescence, but 

 desiccatioa and the change of the affected walls into a tough 

 skin which iu a very remarkable degree presents a median ical 

 obstruction to expansion. 



U. In consequence of the binding of the cuticle, the parenchym 

 of the berries is impeded in its normal growth. 



7. The berries therefore acquire only half their size, and the 

 change which takes place on the maturation of the fruit is very 

 incomplete. 



8. Every individual berry of a bunch, in which the rest are 

 diseased in a high degree, whose cuticle has not suffered under the 

 attack of the fungus, progresses to its normal size, while the 

 non-maturation of the other berries cannot be ascribed to any 

 disease of the plant. 



Whereas on the one side there is not a single sign which 

 indicates a general or local disease of the Vine, and, on the other, 

 observation proves that the parasitic fungus produces a malady 

 on the spots to which it is attached, and since all the phases of 

 the malady are deducible from this affection of the superficial 

 tissue, it follows, as a matter of necessity, that the cause of the 

 Vine-mildew must be assigned solely and entirely to the Grape- 

 fungus. 



If we call in aid a present predominant predisposition of the 

 Vine to the malady to explain the general diffusion of the fungus, 

 which had never been observed before, a point arises which does 

 not admit of dispute, since any sure foundation for the discussion 

 is wanting, inasmuch as this supposed predisposition is not 

 evinced by any especial symptom, but is deducible only from the 

 accidents of the disease, and its diffusion admits of explanation as 

 easily from the assumption that, admitting the perfectly unaltered 

 constitution of the Vine, the progress of the Vine-mildew in the 

 present moment is favoured by causes which are unknown. 

 According to this supposition, which as it appears to me is most 

 accordant with existing phenomena, we shall have as little reason 

 to take into consideration the whole question of the condition of 

 the health of the Vine, as, for example, the pathological condition 

 of our Fir-trees, if the production of millions of caterpillars, by 

 which whole forests have been destroyed, be favoured by certain 

 inexplicable circumstances. 



In the hope that the study of those species of mould which are 

 analogous to the Grape-mildew might throw much light on the 

 peculiar phenomena of tlie disease and its attendant fungus. 



