552 Crown Gall-Animal Cancer Analogy 



virulence exist in the curly-top virus, and the discoveries of this 

 and other factors have given rise to new interpretations placed on 

 the same or similar fundamental phenomena. 



In 1923, when Dr. L. O. Kunkel returned to the United States 

 after several years spent in Hawaii studying diseases of sugar cane 

 and other plants, he accepted a position with the Boyce Thompson 

 Institute for Plant Research at Yonkers, New York, and there 

 performed his valuable studies on the aster yellows. Smith had 

 told him that when he solved the problem of aster yellows he 

 would find the way to solve the peach yellows problem. In 1925 

 in Science ^^ appeared preliminary pronouncements on " Insect 

 transmission and host range of aster yellows," and in 1926, in 

 the American Journal of Botany,^'^ the article, by Kunkel, which 

 Smith read the following January. This was entitled, " Studies 

 on aster yellows," and of it Smith wrote in his diary: 



It is a fine piece of work. He has transmitted the disease to more than 

 50 plants belonging to 23 families, but not to Rosacae or Leguminoseae. 

 In many ways it is like Peach Yellows and Curly Top of beets. It is trans- 

 mitted by a leaf hopper {Cicadula sexnotata) but only after it has fed on 

 diseased plants and then a period of 10 to 14 days must elapse before the 

 hopper can infect plants. 



In 1926 Dr. Simon Flexner was directed by the board of the 

 Rockefeller Institute for Medical Research to go to Europe and 

 investigate the subjects of plant pathology and physiology with a 

 view possibly to establishing a department within the Institute. 

 About 1932 a department was created and Dr. Kunkel was 

 placed in charge of the work which since has been combined with 

 that of animal pathology. One of the great laboratories of the 

 world for the study of virus diseases of plants has been developed 

 under his administration, and the work, of course, has included 

 the study of all plant diseases. The late Dr. William Crocker, 

 former managing director of the Boyce Thompson Institute and 

 himself one of the greatest authorities on plant physiology this 

 country has produced, has this to say in his recent book Growth 

 of Plants ^" of the work of Dr. Kunkel at the Thompson Institute: 



'"•62: 524. 



®^ 13: 646-705, Dec. 1926. The leaf hopper Cicadula sexnotata is now described 

 as Macrosteles divisus Uhler. See Phytopathology 31(2): 120-135, Feb. 1941, and 

 literature cited. 



*" Twenty years' research at Boyce Thompson Institute, 15, N. Y., Reinhold Pub. 

 Corp., 1948. Dr. Kunkel's work is reviewed, pp. 10-15. 



