60 



THE AMEBIC AN NATURALIST 



[Vol. LI 



been used as a stock, but is not popular on the Pacific coast be- 

 cause of its slow growth in the nursery and the difficulty of 

 working it with many of the stone fruits. Duane, P. domestica, 

 Table VII, is being used to some extent as a stock in California 

 and shows resistance to gall in old vineyard land where it has 

 been grown for six years. It makes as large a tree as the popular 

 Myrobolan stock. The seedlings are grown from suckers, which 

 give a root likely to sucker. Reine Claude (green gage) variety 

 has shown resistance and would without doubt be a good stock 

 for the domestic type of plums. P. Armeniaca, variety Mikado, 

 is an apricot that differs somewhat from the one commonly grown 

 in California. It should be tested out experimentally as a stock 

 for apricots to replace the susceptible one now being used. 



The almond, from field observations, is one of our most sus- 

 ceptible stock and this is fully confirmed by the following inocu- 

 lation experiments : Fourteen different varieties of almond seed- 

 lings not summarized in the following tables were inoculated in 

 April of 1913 at the University Farm at Davis, California. 

 These in all cases showed a high percentage of infection. So far 

 the peaches and almonds have shown only slight resistance. 



It will be noted that our most popular stocks as Myrobolan, 

 peach, apricot and almond are very susceptible, which only goes 

 to confirm field observations that the stock used for the stone 

 fruits are very susceptible to crown gall. 



The work so far conducted shows that seedlings of the German 

 and Italian prunes might be promising stock for certain of the 

 stone fruits, probably those of the domestica type. However, no 

 definite recommendations can be given, as the work is now only 

 in its preliminary stages. 



