THE COMMUNICABILITY OF CROWN-GALL. 



23 



Beginning with 1903 plants were grown each year from seed in the 

 manner described on page 14. Some of these were inoculated at the 

 age of from 3 to 6 months by inserting pieces of living grape root galls 

 into wounds at or below the surface of the soil. Others were wounded 

 without inoculations and set aside as a control. The results of these 

 inoculations were negative in many instances. A summary of the 

 results of these experiments for five years is given in Table IV. 

 Both European and American varieties of grapes were used. 



Table IV. — Summary of the results of inoculating seedlings of various kinds of plants 



with grape crown-gall, 1903-1907. 



The results of the experiments prove the communieability of the 

 grape crown-gall (14.5 per cent) with pieces of galls. They also 

 show that the disease is communicable as follows: To the almond, 

 8.8 per cent; blackberry, 4.8 per cent; cherry, 20 per cent; peach, 

 30.1 per cent; and raspberry, 4 per cent. The inoculations on the 

 apple, apricot, chestnut, pear, and plum gave negative results. 



Another set of experiments was conducted similarly with grape 

 seedlings, except that the inoculations were made with galls from 

 other host plants. Table V shows the results: 



Table V. — Summary of the results of inoculating grape seedlings icith galls from other 



host plants. 



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