i9io.] 



"Crown-gall" in England. 



619 



a species not previously described, and that Tourney's 

 Myxogaster is but a secondary agent. It seems quite certain 

 that the galls investigated by Tourney and by Smith and 

 Townsend are identical in origin. It is also quite certain 

 that the "crown-galls" met with in England exhibit the 

 Dendrophagus described by Tourney, and that in these no 

 trace has yet been met with of B. tumefaciens, as described 

 by Smith and Townsend in Centralbl. f. Bakt. Parasit. u~ 

 Infektionskr., xx., p. 89 (1907). 



From the economic standpoint, however, this variation in 

 the experience of different workers does not materially affect 

 the problem. It is not open to dispute that "crown-gall " 

 is caused by the presence of a living organism. It is there- 

 fore possible to formulate definite preventive measures. 

 Further, it is admitted by all who have investigated the subject 

 that the affection, whatever its precise cause, is contagious. 

 Nurserymen and fruit growers will on this account doubtless 

 be glad to adopt such measures as are required to prevent the 

 wholesale dispersion of the disease. 



The disease is probably not new to this country, nor to- 

 other European countries, as descriptions of galls correspond- 

 ing in appearance and position on the host-plant with, 

 "crown-gall" are described in works on plant pathology. 

 Sorauer, who made some observations on such galls in 

 Germany, noticed that they were much more frequent in 

 some nurseries than in others, which indicated a parasitic 

 origin, but not succeeding in finding the parasite, he con- 

 sidered such galls as probably the result of mechanical injury 

 or some physiological disturbance. We have at present no- 

 knowledge of the relative frequency of "crown-gall" in this 

 country. The galls are formed just underground, and thus 

 escape observation, and those galls that have been observed 

 from time to time have had their origin attributed to other 

 than the true cause, and have not been considered as the 

 symptom of a dangerous disease. 



"Crown-gall" is most destructive to nursery stock, as the 

 disease spreads rapidly along the rows, killing a large 

 number of the seedlings outright. The widespread dis- 

 semination of the disease in the United States is attributed 

 to the wholesale distribution of infected stock from nurseries, 



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