PLANT CANCER 



The immense protuberance on the above sugar-beet was caused by a plant-disease known as 

 Crown Gall; it was produced artificially in this case by inoculation with the bacteria. 

 In the symptoms and development of this disease there is a remarkable similarity to human 

 cancer. Crown Gall frequently causes the formation of unusual numbers of very fine roots; 

 this gives another common name, "Hairy Root." A large variety of trees and shrubs 

 are subject to this disease, which may appear either on the roots or on the branches; truit 

 trees are particularly susceptible to attack. Few people realize that bacteria may cause 

 sickness in plants as well as animals. Photograph by courtesy of Dr. Erwin t. bmith. 

 (Fig. 8.) 



