22 FIELD STUDIES OF THE CROWN-GALL OF THE GRAPE. 



Wounded control plants of the same species remained free from the 

 disease. This investigation established the relationship of a number 

 of gall diseases and the cause of the crown-gall of the peach, etc. No 

 inoculations were reported at this time on grapevines, but Doctor 

 Smith informs the writer that one successful inoculation was made 

 on the grape, April 3, 1907, and that 18 successful inoculations were 

 obtained in May of that year (all that were inoculated). 



During the first week in April, 1907, an organism similar to the one 

 found in 1903 was isolated by the writer from grape root galls and 

 inoculations were made into healthy peach, apple, and apricot seed- 

 lings during the second week in April. Of 14 peach seedlings inocu- 

 lated 9 became diseased with galls at the point of inoculation; of 

 12 apricot seedlings 6 became similarly diseased; of 5 apple seed- 

 lings inoculated none became diseased. The final count was made 

 on November 5, 1907. Wounded control plants of the same kind 

 remained free from disease. 



In December, 1908, at a meeting of the Botanical Society of 

 America, Doctor Townsend (51a) reported the results of further experi- 

 ments with the organism from the Paris daisy. This organism when 

 kioculated into other plants produced galls on the tomato, potato, 

 tobacco, sugar beet, hop, carnation, grape, raspberry, peach, and 

 apple. This proves that galls on the grape may be produced by 

 Bacterium tumefaciens and are identical in origin with those on a 

 number of other plants. The galls obtained on the grape by Town- 

 send were both on the canes and roots, and resembled in form the galls 

 on the roots of the grape. 



THE COMMUNICABILITY OF CROWN-GALL. 



OBSERVATIONS BY OTHER INVESTIGATORS. 



Very little has been published on the communicability of crown- 

 gall, except in the line of opinions by observers. These will not be 

 cited. 



Lataste (34) communicated the disease to the root of a growing 

 grapevine by binding a piece of living grape gall over a wound. 



RESULTS OF EXPERIMENTS. 



Experiments with seedlings. — In 1908 the writer (30) published the 

 results of part of a series of experiments on the communicability of 

 the crown-gall from a number of host plants, showing that the dis- 

 ease is communicable from pieces of living tissues of soft crown-galls 

 placed in wounds on the roots of the host plants. These experiments 

 proved the identity of the soft galls of the apple and pear with 

 those of the stone fruits, raspberry, blackberry, and rose. A portion 

 of these experiments was devoted to the communicability of the 

 grape crown-gall. The results of these and other experiments will 

 now be given. 



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