2l6 



AMERICAN VINES. 



altogether suit the stock, which, being therefore placed 

 under unfavorable conditions, develops less, suffers, and 

 becomes weaker. * The disturbances manifested after grafting 

 are,, therefore, the result of the internal or external indi- 

 vidual physiological differences existing between stock and 

 scion. These disturbances can only be noticed in varieties 

 differing from each other, but never occur in the case of a 

 variety grafted on its own roots. The Folle-blanche, 

 grafted on its own roots in difficult soils, behaves 

 exactly as if ungrafted; it is not more affected by 

 chlorosis, its development and fructification are identical. 

 Therefore, the greater the analogy existing between the 

 functions of stock and scion and their mode of living, the^ 

 less marked will the effects of grafting be. We have seen 

 that European varieties grafted on the species of Musca- 

 dinia are successful, but that, grafted on Ampelopsis or 

 Cissus, they die soon after knitting. With Riparia, etc., the 

 physiological functions of which are so different to those of 

 European vines, these phenomena are still very marked ; 

 they are less marked with other stocks which, for some 

 reason or other, are more closely related to Vinifera, and this 

 explains why these disturbances are greatly attenuated with 

 Franco-American graft-bearers. 



It is very difficult to define exactly the differences of 

 affinity ,of various American stocks for a given scion, as also 

 to ascertain if the differences of vegetation are due to pro- 



* Lucien Daniel (Comptes Rendus, aist September, 1891) arrives at similar 

 conclusions for plants other than vines: 



"It seems strange to see plants similarly closely related to the genus Tarax- 

 acum, such as Barkansia, Lettuce, and Chicory, behave differently; the first 

 grafting successfully, the two other knitting well, but dying if their adventive 

 roots are removed. 



"Anatomical studies may explain this anomaly. The roots of the Taraxa- 

 cum are gorged with inuline; this substance passes through the membranes of 

 the Barkansia, which assimilates it, as may be ascertained by microscopical 

 -examination of tran verse and longitudinal sections of the graft; both stock and 

 scion contain inuline. 



"But inuline does not penetrate the scions of Lettuce or Chicory; it has 

 never been detected in them. Therefore, they wither or die, if supplementary 

 food is not given to them through their adventive roots. This is' not an isolated 

 case. We may understand that the membranes of some scions are imperme- 

 able to certain matters elaborated by the stock, in the same way as Lettuce and 

 Chicory are _ impermeable to inuline. The failure of many grafts may thus be 

 easily explained by a phenomenon of insufficient nutrition, without having 

 recourse to problematic affinities between genera and species. ' ' 



These remarks by Daniel apply still more forcibly to the vine and its grafts. 

 It is because the matters elaborated by the scion cannot be assimilated by the 

 stock that the' latter remain weak, and eventually its weakness affects the 

 whole plant. But is it simply because the membranes of the stock do not allow 

 these substances to pass through that they remain unassimilated? If it is so, 

 it is apparent that before the grafting these substances were unnecessary to the 

 ^stock, and that afterwards they become inimical to its development. 



