2 



Mycologia 



about by Bacterium tumefaciens Hedgcock does not state. He 

 claims however with Tourney that the galls die annually. In a 

 later study (1910 2 ) of crown gall on the apple he maintains that 

 the destructive effect of this disease is overrated. 



Smith (1911-12) in his extensive studies on crown gall and its 

 resemblance to animal cancer shows that the physiological effects 

 of these tumors vary from species to species and also within the 

 species and are generally less pronounced and speedy than one 

 might expect. He holds that it is difficult to show conclusively 

 that the substances produced in the tumor by the parasite are 

 absorbed and act as slow poisons. This is especially difficult in 

 view of the fact that the galls are often soaked by rains and be- 

 come infected with other parasitic and saprophytic organisms. 



Levin and Levine (1918-20) in a report on the malignancy of 

 the crown gall and its analogy to human cancer pointed out that 

 a number of the phenomena in both diseases are analogous. They 

 contend that the neoplasms in plants produced by Bacterium tume- 

 faciens are sometimes benign though some are true malignant 

 growths. The latter generally dwarf the plant so affected and 

 cause necrosis of the tissue above and below the gall. 



These studies and those of Smith's and other workers were 

 carried out in annuals, biennials or deciduous trees in which the 

 period of growth of the host as well as the crown gall is normally 

 interrupted. The difficulty in determining whether toxins are 

 present in such cases is made more difficult by the intervention 

 of natural death, caused by changes in temperature and its con- 

 comitant factors, and second, by the occurrence of infections 

 caused by fungi and even insect grubs, the eggs of which are 

 deposited in the soft tissue of the young crown gall. 



The purpose of this report is to bring forward further evi- 

 dence on the malignancy of the crown gall experimentally in- 

 duced on mature evergreen perennials such as the common rubber 

 tree, Ficus elastica. In such plants where the growth is rather 

 active all the year round, when kept under uniform, green house 

 conditions, the effect of the crown gall organism and the neo- 

 plastic growth on the host can be kept under observation for an 

 extended period. Drenching rains and destructive insects are 



