Rfsearch on Plant Tumors 515 



the Royal Botanical Garden, Kew, would be transferred iii 1919 

 to Rothamstcd Experimental Station, Harpenden, and an Institute 

 of Plant Patholot;y, with W. h. Brierlcy in charge of a mycological 

 department, be created. July 15, 1919, Brierley would write to 

 Smith, 



Crown Gall as described in your investigations has had practically no 

 attention paid to it in this country and in consequence 1 have asked Dr. 

 Henderson Smith to carry out some experimental work upon it. Dr. Smith 

 is a medical patholoi^ist of some eminence and was until lately in charge 

 of the bacteriological department of the Institute of Preventive Medicine. 

 He is now devoting himself to the study of bacteria in relation to plant 

 disease and in future will be working here with me. 



Brierley sent for both cultures and literature. 



In 1915 ^" Ralph Eliot Smith, professor of plant pathology at 

 the University of California, had written: " It is scarcely twenty 

 years since Erwin Smith challenged the skepticism of the European 

 world in regard to the existence of bacterial plant diseases. Still 

 more recent has been most of the development of knowledge of 

 protozoa, spirochetes, sporozoa, and filterable viruses in animal 

 pathology. With these examples before us," he asked, " who 

 shall say that organized living parasites of wholly unknown types 

 do not exist .'^ " 



Insisting that our " knowledge of parasitism, either in plants 

 or animals, is by no means exhausted," he maintained that " In 

 the present status of plant pathology the following broad principle 

 cannot be denied: ' There is no single instance of a positively 

 demonstrated inciting cause of any specific plant disease except a 

 parasite.' We have theories, indications, appearances, and effects 

 which point otherwise, but of proof we have none in any case." 



His real plea was for renewed investigation of many of the 

 obscure " physiological " plant diseases on the basis of their 

 cytology and histology, all changes of structure as far as possible 

 detected from the disease's inception and followed through its 

 effects. "Animal pathologists long ago," he urged, 



arrived at cellular pathology as the last resort in diagnosis, and the plant 

 pathologist can do no less if he would solve his most obscure problems. . . . 

 Let one read the recent edition of Mallory's Pathological Histology, written 



"The investigation of " physiological " plant diseases, Phytopathology 5(2): 83, 

 87, 90, Apr. 1915. 



