28 



CAUSE AND NATURE OF CROWN-GALL 



trees which grew in rows 20 to 22, inclusive, which were treated 

 to minced galls and the mixture of Milestone, copperas, and 

 quicklime. 



Twenty-three of the forty-two trees obtained from rows 23 

 to 29, inclusive (almond, peach, and apricot, treated with 

 minced almond galls), were badly infested with crown-gall. 

 The percentage of diseased trees was in the order of almond, 

 apricot, and peach, the peach being the least diseased of the 

 three. Fig. 8 is a photographic reproduction of all the trees in 

 row 25 in the order in which they grew. 



No galls were found upon the 

 fourteen specimens of English 

 walnut which grew in rows 30 

 and 31, the nineteen seedling 

 grapes obtained from row 33, or 

 the seven apple seedlings from 

 row 34, although each row re- 

 ceived an equal quantity of the 

 minced galls. The prunes failed 

 to'germinate. An indefinite num- 

 ber of seeds were planted in rows 

 33 and 34, but the greater number 

 did not germinate. 



EXPERIMENTS IN GROWING SEED- 

 LINGS IN POTS FILLED WITH 

 CRUSHED QUARTZ. 



In January, 1899, six large 

 pots, each containing about one- 

 half cubic foot of finely crushed 

 quartz, were planted with al- 

 monds. The almond seeds used 

 for planting were carefully re- 

 moved from the shells and ten 

 seeds planted in each pot. In 

 three pots minced galls were placed with the seeds when planted. 

 When harvested, in November, 1899, no diseased seedlings were 

 obtained from among the sixteen plants in the check pots, but 



Fig. 9. — Diseased almond seedlings 

 grown in pots of crushed quartz, in 

 which were placed small pieces of the 

 gall. 



