414 



BACTERIAL DISEASES OF PLANTS 



frequently decays readily, especially on soft plants like the sugar 

 beet and the willow (Figs. 321, 322). The nature of the very 

 large hard tumors on oak trees common in the United States is 

 still undetermined. The largest crown-gall I have ever seen 

 weighed 96 pounds; this was received in 1919 by Dr. B. T. Gal- 

 loway and is now in our collections. It was found on the stem 



FIG. 316. Dwarfing effect of crown gall on sugar-beet. Pure-culture in- 

 oculation. The organism used was plated from a gall on Paris daisy. Tumor 

 larger than the root. Time. 37 days. Inoculated June 3, 1907. ^ nat - size. 



of a wild fig on an island in the Florida everglades 40 miles 

 southwest of Miami (Florida State Park). Dr. I. B. Pole 



Yl nat. size. A serious disease of roses. (3) On apple limb. Above-ground 

 tumors one growing out of pruned end. From an apple tree in North Carolina. 

 1911. % nat. size. Often the entire tree is attacked in this manner. (4) 

 On a pear seedling grafted by Hedgcock with fragments of a rose-gall in the sum- 

 mer of 1907. Photographed December 23, 1907. % nat. size. See next page. 



