114 FUNGOUS DISEASES OF PLANTS 



IV. CROWN GALL OF APPLE, PEACH, AND OTHER PLANTS 

 Pseudomonas tumefaciens Erw. Smith and Townsend x 



Hedgcock, Geo. G. Crown Gall, Hairy Root Disease of the Apple. Bureau 



Plant Industry, U.S. Dept. Agl. Built. 90 (Pt. II): 15-17- pk. 3-5. 



1906. 

 Hedgcock, Geo. G. The Cross Inoculation of Fruit Trees and Shrubs with 



Crown Gall. Bureau Plant Industry, U. S. Dept. Agl. Built. 131 (Pt. Ill): 



21-22. 1908. 

 Schrenk, H. von, and Hedgcock, Geo. G. The Wrapping of Apple Grafts 



and its Relation to Crown Gall Disease. Bureau Plant Industry, U. S. 



Dept. Agl. Built. 100 (Pt. II): 5-12. 1906. 

 Selby, A. D. Diseases of the Peach. Ohio Agl. Expt. Sta. Built. 92 : 208- 



217. pis. 5-6. 1898. 

 Smith, Erw. F., and Townsend, C. O. A Plant Tumor of Bacterial Origin. 



Science, N. S. 25 : 671-673. 1907. 

 Toumey, J. W. An Inquiry into the Cause and Nature of Crown Gall. Ariz. 



Agl. Exp. Sta. Built. 33: 1-64. figs. 1-31. 1900. 

 Townsend, C. O. A Bacterial Gall of the Daisy and its Relation to Gall 



Formations on Other Plants. Science, N. S. (Abstract) 29 : 273. 1909. 



Occurrence. The crown gall has thus far been found most 

 commonly upon rosaceous plants (Rosaceae), among these being 

 included practically all of the stone, pomaceous, and bush fruits 

 of this family, especially the various species of Prunus, Pyrus, 

 Rubus, and Rosa. It has, however, been reported upon a variety 

 of other plants, such as the grape (Vztis spp.), walnut {Juglans 

 nigra), chestnut (Castanea dentata), poplar (Populus alba), willow 

 (Salix), etc. Thus far, very little striking varietal resistance has 

 been reported, although it is probable that the almost total absence 

 of the disease under certain conditions is to be attributed in part 

 to the difference in the susceptibility of the hosts as well as to 

 diversity of external conditions. In general, nursery stock is 

 more readily affected than older trees ; but this may be due to 

 greater opportunity for infection. 



1 It seems justifiable to give as conclusive the evidence thus far presented re- 

 garding the bacterial nature of the widespread crown gall. This evidence has been 

 published by Smith and Townsend only as a preliminary paper and as abstracts of 

 reports (one cited in the literature above) read before two societies at the meeting of 

 the American Association for the Advancement of Science, and Affiliated Societies, 

 Baltimore, December, 1908. The data and proofs orally presented, however, leave 

 no reasonable doubt as to the bacterial cause of a large number of gall formations. 

 It is not yet clear whether the galls of all such plants as apple, peach, grape, etc., 

 are due to the particular species here described, or to closely related species. This, 

 however, is a matter of far less present significance. 



