WARTS ON THE BACK OF THE LEAF. 



57 



and arrest the growth of all they attack. In a hot and 

 rather dry climate they never can do this, and in such 

 the vine may be considered safe from their effects. 



WARTS ON THE BACK OF THE LEAF. 



This is a sort of conglomerate of little green warts 

 that form on the lower surface of the leaf, as if the 

 result of an extravasation of sap through its epidermis 

 or skin. Some writers say this is not a disease. If it 

 is not such, strictly speaking, it is at least organised 

 matter in the wrong place ; and I am confident it seri- 

 ously impedes the important functions of perspiration, 

 digestion, and respiration ; so that if not in itself a 

 disease, it leads to functional derangement, which is 

 nearly the same thing. As has been remarked while 

 treating of the effects of sulphur, these green warts are 

 more easily affected by the particles thereof floating in 

 the atmosphere of the vinery than any other portion of 

 the vine, except the embryo berries. 



I can undertake to produce or prevent this disease — 

 shall I call it 1 — at any time betwixt the first expansion 

 of the foliage and the stoning of the fruit. A close, 

 warm atmosphere, saturated with moisture, will pro- 

 duce it ; whereas a free circulation of air, moderately 

 charged with moisture, will prevent its appearance. I 

 have seen instances where the leaves were so affected 

 by it that they all cupped themselves up round the 

 edges, the fruit did not swell to much more than half 

 - its natural size, and the general progress of the vine 

 was retarded. 



