THE RECIPROCAL INFLUENCES OF STOCK AND CION 583 



January, 1913, there were in this nursery, at the same elevation and under the 

 same conditions, yearling lemon tops on sour stock (buds had been inserted 

 several inches above the ground) alongside of sour seedlings. While a shght 

 injury to the foliage was the only harm experienced by the latter, the lemon 

 tops were killed, and the frozen wood extended 3 to 4 inches down on the sour 

 stock. Similar conditions were found on pomelo stock while the pomelo seedlings 

 were scarcely touched. "^^^ 



Other Influences. — Sahut states that quince roots topworked to pear 

 are more particular in their soil requirements than those not worked over; 

 they require a more fertile soil. However, as he indicates, the general 

 rule is to the contrary; otherwise the selection of lime resistant, drought 

 resistant and moisture resistant stocks would be to no point. The cion 

 itself does not render the stock subject to phylloxera or immune to 

 woolly aphis, though a lack of congeniality may induce weakness and 

 hence a lack of recuperative power. The transmission from cion to stock 

 of variegation has been discussed previously; it cannot be regarded as an 

 instance of true influence exerted on the stock by the cion. 



In General. — Just as in the case of stock on cion, in considering the 

 influence of cion on stock it is not necessary, so far as fruit plants are 

 concerned, to predicate any direct effect other than on vigor. Every 

 other influence that has been established or attributed can be explained 

 as exercised indirectly through vigor and can be placedoon a quantitative 

 basis. This action on vigor may be direct when the two parts to the 

 graft are congenial and make a good union, or it may be indirect when 

 there is apparent uncongeniality and the union is poor. Qualitative 

 influences, such as the passage of alkaloids across the graft, or the barring 

 of inulin by the graft, are not necessary to explain any observed phe- 

 nomena resulting from grafting in fruit plants. 



