CHAPTER II 



GALLS AND TUMORS 



CROWN GALL 



Pseudomonas tumefaciens. Erw. Smith and Townsend 



Crown gall is one of the most recent plant diseases to be traced to 

 bacterial origin. Its occurrence is so common in nursery stock that in 

 a certain Western State, 75 per cent of the young trees and shrubs 

 condemned by nursery inspectors are condemned for crown-gall, and 

 Tourney places the annual loss to orchardists at $500,000 to $1,000,000. 



FIG. 198. Crown gall with hairy root on nursery stock. Northern Spy apple. 



(After Paddock.) 



HISTORY. Smith and Townsend* working with the gall of the Paris 

 daisy observed bacteria in these outgrowths in 1904, but it was not 

 until 1906 that they succeeded in isolating the causal organism and 



* Smith, Erw. P., and Townsend, C. O., "A Plant Tumor of Bacterial Origin," Science, N. 

 S. Vol. XXV, No. 643, p. 671-673, 1907; "The Etiology of Plant Tumors," Science, N. S. 

 Vol. XXX, No. 763, p. 233, 1909. 



Townsend, C. O., "A Bacterial Gall of the Daisy and Its Relation to Gall Formations on 

 Other Plants," Science, N. S. Vol. XXIX, p. 273 (Abstract), 1909. 



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