OBSERVATIONS ON SOME VINE DISEASES IN SONOMA COUNTY. 23 



grapes. The Grape-shrivel had destroyed the four or five tons of fruit 

 that the showing of the vines in June would have led one to expect. 



Cause of the Grape-shrivel. From the description of the Grape-shrivel, 

 and the manner and circumstances under which it develops, it is evident 

 that the disease is a peculiar manifestation of imperfect nutrition. The 

 yellowing and dying of the leaves, beginning at the base of the shoots, 

 is characteristic of vines suffering from want of water. Premature 

 ripening is also a consequence of lack of water. The fact that the 

 grapes shrivel, often previously to the discoloration and wilting of the 

 foliage, does not invalidate this contention; for, it may be shown that 

 under the influence of drought, or a paucity of free water in the soil, the 

 fruit of the French prune will shrivel even when the foliage is healthy 

 and luxuriant. It is, therefore, no stretch of the imagination to suppose 

 that the same phenomenon happens in the case of the vine. In fact, in 

 several cases we have obtained experimentally the characteristics of the 

 Grape-shrivel as shown in the grapes. Our experiments, though crude 

 enough, were quite instructive. We severed, in healthy vines, several 

 long canes bearing vigorous shoots carrying well-developed bunches of 

 grapes. Almost immediately after the canes were severed the shoots 

 began to wilt, as one would expect. The bunches of grapes, however, 

 generally wilted as they do in the case of the Grape-shrivel: the lower 

 bunches on a shoot would frequently dry out faster than the others. 

 We also observed that the pith discolored in the neighborhood of the 

 diaphragms first, and that the wood tissue became discolored. 



The discoloration of the pith in the shoots, and the discolorations in 

 the spurs, arms, and trunk, may be shown to occur in vines under very 

 varied and divers circumstances, and are, therefore, at most of but 

 secondary importance. 



The symptoms of the Grape-shrivel, then, are those of a vine suffering 

 from drought. This is further emphasized by the following facts: 



The Lenoir, the stock upon which the Semillons are grafted, is not 

 very resistant to the Phylloxera. Its rootlets (which, the reader will 

 bear in mind, are the active agents in the absorption of water) were 

 much distorted by the Phylloxera, and their functions, therefore, inter- 

 fered with. This fact explains how it is that a vine grafted on Lenoir 

 (or any other stock sensitive to the Phylloxera) could suffer from want 

 of water, even when the soil contained nine or ten per cent of free 

 moisture. But it may be asked, why does the non-grafted Lenoir not 

 suffer ? This question is easily answered. The Lenoir is not as vigor- 

 ous a grower nor as heavy a bearer as the Semillon. When it bears 

 the Semillon, then, or any other vinifera more vigorous than itself, its 

 rootlets, even when not preyed upon by the Phylloxera, are unable to 

 take up and transfer to the graft its optimum of food; and the bigger 



