EXPERIMENTS WITH THE APPLE ORGANISM. 95 



Result -J iinmiry 5, 1911: Typical small galls (i'l. XXXV, lig. J) 

 have appeared in a portion of the needle priclvs on 4 of the 6 plants, 

 5 shoots, 14 galls in all. 



RELATION OF SO-CALLED HARD-GALL OF APPLiE TO SOFT-GALL. 

 BOTH KINDS OF CROWN-GALL DUE TO BACTERIA. 



Doctor Hedgcock has distinguished between hard and soft gall of 

 the apple. He has not pointed out any good means of separating the 

 two, but has stated the more common hard-gall to be noninfectious. 

 As a matter of fact, the two Idnds of tumors under consideration 

 intergrade and both are due to bacteria, the differences being refer- 

 •dhle probably either to variation in the rate of growth of the host 

 ])lant or else to varying degrees of \drulence on the part of the bacteria, 

 perhaps to both of these factors. 



APPLE-GALL (HARD AND SOFT) ON VARIOUS PLANTS. 

 PRELIMINARY ISOLATIONS AND INOCULATIONS OF 1908 (bROWN) . 



On October 15, 1908, an apple seedling %vith a gall IJ inches in 

 diameter was found among trees purchased by the De])artment of 

 Agriculture to be used for the congressional distribution. An 

 organism very much hke the daisy gall organism in appearance and 

 manner of growth was plated from this gall. Inoculations into 

 apple trees, peach trees, daisy plants, and sugar beets produced 

 galls in each species, although the per cent of infections was low. 



On November 25, 1908, apple-galls were received from a nursery 

 in Maryland. Plates were poured from the softest of these knots 

 and the same organism obtained as before. 



On November 27, 1908, Dr. G. G. Hedgcock brought in some of 

 his so-called hard-galls of ai)ple and challenged us to plate out the 

 gall organism from them. These, as well as those used for the pre- 

 vious work, were galls without the accompanying tufts of roots 

 (hairy-root). Plates were poured. Colonies resembhng the gall 

 organism appeared on the plates, and inoculations into sugar beets 

 proved that it was the gall-forming organism, for in 18 days galls 

 were produced at the inoculated places. The plants were from the 

 vicinity of Washington (second D. C. test). 



On November 4, 1908, Doctor Hedgcock also sent hard-galls of 

 apple from Iowa to Doctor Smith, asking that tests be made. Miss 

 Brown plated out what seemed to be the gall organism from one of 

 these plants, but no inoculations were made by her. For result of 

 independent isolations and inoculations into daisy by Doctor vSmith, 

 see inoculations of November 9, 1908. 



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