40 UNIVERSITY OF CALIFORNIA. 



grafts where too much watering has been indulged in. In sand that is 

 kept slightly moist, on the contrary, the best results are found. 



On the other hand, aeration assists greatly in the formation of callus. 

 Growing cells respire more than is ordinary for older ones, and hence 

 they require a medium that is especially well supplied with oxygen. 

 We note, therefore, that grafts that are deeply buried in very compact 

 soils will scarcely callus at all. 



(b) Effects of Grafting; Affinity. It is a general rule that there is 

 an enfeeblement of the graft, except in the case where the graft and the 

 stock are of the same variety; and it is also a fact that this is accom- 

 panied with an excessive fructification of the grafted vine, especially 

 where the enfeeblement is most marked. Together with the excessive 

 fructification is noted a production of a greater number of bunches which 

 are larger than the normal; also, larger and better nourished berries of 

 earlier maturity and a greater richness in sugar. 



Another important item in this case is the fact that there is always 

 less " coulure." On the other hand, with the enfeeblement of the vine 

 by grafting, while the crop is benefited, there is noted an increased 

 susceptibility to the phylloxera, as well as swellings of more or less size 

 at the joint of the graft with the stock. The effects of the graft are 

 similar to that of the annular incision so much practiced in hothouse 

 grape culture to give size and sweetness to the grape. At the same 

 time, while the results are similar, there is quite a difference in the 

 causes. Beyond a mere interruption of sap in the case of the annular 

 incision, the similarity ceases. In the one case it is a temporary wound, 

 causing an interruption of the reflux of the sap; while in the other there 

 is a lack of harmony in the functions of the various parts of the plant, 

 which brings about the same effect as the annular incision. 



There is a difference in vigor only when the variety of the graft and 

 of the stock differ, otherwise it is but a wound that will rapidly heal up 

 and leave the vine as it was before. The greater the difference in 

 variety, the greater will be the difference in effects. A graft of the Vitis 

 Vinifera on the group of the American species called Muscadina, may 

 grow for a time, but the graft is so badly nourished that it soon perishes. 

 The same is true in the case of grafts on the Ampelopsis, Cissus, etc. 

 On the Vitis Riparia, the physiological functions of which are quite 

 different from those of the Vitis Vinifera, the difference in vigor is quite 

 marked. They are less in the cases of the other resistant stocks which 

 approach more closely the Viniferas. In the case of the Franco-Amer- 

 ican hybrids these differences are still less. 



The chemical composition of the Franco- American hybrids is the same 

 in the case of grafted vines and non-grafted ones, which furnishes us 

 with an indirect proof of the greater affinity of the Franco- American 

 hybrid for the Vitis Vinifera than in the case of the American stocks, 

 which do show a chemical difference in composition between the grafted 

 and the non-grafted vines, as well as greatly diminished vigor. Allow- 

 ance being made for resistance to the phylloxera, it will be seen that there 

 is greater affinity between the Franco- American hybrids than between 

 the pure species. But it is to be noted that the various European vari- 

 eties do not always behave alike on the same stock. The Cinsaut does 

 badly on the Riparia, while the Carignan does better than the Aramon on 

 theLenoir and Riparia. The Clairette is one of the varieties of the Vitis 



