282 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 



grove of navel oranges was found where every other tree in the row 

 had a lemon trunk. In parts of this grove the trees with the lemon 

 trunks had lost two or three times as many leaves as the trees with 

 the orange trunks. Numerous other cases were found where orange 

 trees with lemon trunks were injured more than similarly situated 

 trees with orange trunks, but the reverse of this sometimes occurred, 

 so that no positive rule can be stated. It is, however, pretty clearly 

 evident that it is, in general, poor policy to top work lemons to oranges. 



Influence of Roots or Stocks. It has been claimed that the root- 

 stock on which the tree is budded may affect the resistance of the top. 

 The stocks that have been most used in California are the sweet orange 

 and the sour orange. In general, no difference in the resistance of 

 the trees on these two stocks could be found. 



In one rather large nursery, containing both sweet and sour seed- 

 lings, all the trees were killed to the ground in January, but on 

 June 12, 1913, a count of several hundred trees of each variety showed 

 that 71.3 per cent of the sweet and 71.2 per cent of the sour trees 

 were recovering, and new sprouts several inches long were growing 

 from the young trunks near the surface of the ground. 



Comparative Resistance of Sweet and Sour Stock 



Pomelo stock has been used by many growers, but no cases were 

 found where the trees on this stock were noticeably different from 

 those on other stocks. 



In one young lemon grove the trees on trifoliate orange roots were 

 hardier than the trees on sour orange roots. At least one case was 

 observed in California where navels on trifoliate stock appeared to 

 be distinctly less injured than navels on sweet stock planted at the 

 same time and in the same grove and having the same treatment. 

 In general, it may apparently be concluded that the trifoliate stock 

 has a tendency to render orange budded on it rather more hardy, but 

 that the difference is slight. 



In some cases there is apparently a definite influence of the tops 

 upon the stocks. In one case, in the spring of 1912, a nursery of sour 

 seedlings was budded to Eureka lemons. Many of these buds did 

 not take, so that during the freeze of January, 1913, there were in 

 this nursery, at the. same elevation and under the same conditions, 



