220 Investigations in Plant Pathology 



the known bacterial plant diseases were treated in a single docu- 

 ment. The work was divided into three classes: those diseases so 

 established that a causal organism had been isolated from the 

 diseased tissue, cultivated in pure cultures, inoculated into a 

 healthy susceptible host plant, and the disease reproduced and 

 an identical organism taken from inoculated vegetable tissue, 

 in other words, those diseases in which the celebrated canons of 

 Koch had been thoroughly satisfied; second, those diseases in which 

 specific organisms had been found, but the evidence was not fully 

 conclusive that Koch's canons had been strictly complied with; and, 

 third, Russell listed those plant diseases which probably were of 

 bacterial origin but not definitely proven. 



Smith later praised Dr. Russell's experiments, especially their 

 " merit of being properly performed, i. e. with sterile juices and 

 pure cultures so that the conditions under which the experiments 

 were made [could] be reproduced by other investigators." His 

 praise was not unqualified,^^ and he found that Professor W. 

 Migula had reviewed the subject in 1892 " briefly but somewhat 

 carefully." Others ^^ had written on bacterial diseases of plants. 

 Julius Wiesner, a year after Russell's experiments were performed, 

 made some experiments as part of an attempt to classify plants, 

 but cultures were not used and the juices not sterilized by filtration. 

 During the spring of 1892, Charles O. Whitman, then recently 

 appointed professor of zoology at the new University of Chicago, 

 offered Russell the chance to continue his researches in bacteria of 

 the deep sea at the Marine Biological Laboratory at Woods Hole, 

 Massachusetts, and in 1893 he was appointed fellow in bacteri- 

 ology at Chicago University. The environment was biological 

 rather than medical, and his thesis, published by Johns Hopkins 

 University in 1892, possessed the added distinction of being the 

 first submitted for the degree of Doctor of Philosophy under 

 Welch. Professors Martin, Brooks, and Welch conducted Russell's 

 doctoral examination, and Welch acquired a knowledge of plants 

 sufficient for the purpose from Dr. John P. Lotsy, a Dutch botanist, 

 who became a university associate in biology and was then domg 

 some studying in his laboratory. February 28, 1893, Russell sub- 



««The bacterial diseases of plants: a critical review of the present state of our 

 knowledge, Amer. Naturalist 30(356): 629-632, Aug. 1896. 



"Erwin F. Smith has reviewed the early works of writers on this subject, 

 Bacteria m relation to plant diseases 2: 9-12 ff., Carnegie Inst. Washington, 1911. 



