FuRTHi^R Ri;siiARcnus IN Disi-Asus OF Plants 5*>3 



years, new extensions of learning; have been hrouL;lit about, and 

 new interpretations have been phiced on some of the factual data. 

 The important points to remember are his studious interest and 

 abundant enthusiasm to know as much as possible concerning dis- 

 eases of man, animals, and plants. A biography of him can only 

 indicate the wide scope of his knowledge. Dealing with so many 

 ditlering problems in plant pathology, he had to acquire much 

 learning of animal and human pathology. For instance, when he 

 and Miss Brown studied the tomato streak virus disease and dis- 

 covered " a curious body (30 and 40/x in diameter) in cortex cell 

 of a tomato petiole close to a streak spot," he carefully described 

 their findings and illustrated these by drawing six differing 

 positions v/ithin range of the nucleus taken by the organism at 

 various times. Then, five days later, Kunkel, recently arrived in 

 Washington from Hawaii, brought with him " stained slides of 

 maize and Hippeastrum mosaic," and Smith learned from him 

 his technique of studying the " problematic bodies " there found 

 "' usually attached to the nucleus." These seemed to have the 

 " structure of protoplasm and often contain[ed} small normal dark 

 staining bodies ht pairs." In his diary memorandum, he wrote, 

 " They are most abundant in parts most badly diseased and look 

 to me as if they might be parasites, yet they do not disorganize 

 the nucleus, though sometimes they make it stain differently." 

 Kunkel told him that " in corn mosaic the diseased cells have 

 very active streaming movement on plasma strands." Again he 

 drew a picture of a " vacuolate problematic body," and asked 

 himself, " Is it a protozoan.^ " But no answer or further opinion 

 was suggested. 



Today, these " x-bodies " found in cells of certain plant virus 

 diseases are presumptively regarded as concentrations of virus 

 particles. During the 1920's, research in virus diseases of plants 

 began to take on definitely the stature of a highly specialized 

 branch of experimental science, inquiring into the nature of virus 

 infection, the various viruses and the species and families of plants 

 susceptible to each virus, the ways and vector agents of trans- 

 mission of plant virus diseases including study of hereditary 

 transmission of diseases from one generation to another; in other 

 words, full-scale research in another class of plant maladies. 

 Cytological and histological investigations became the rule, not 



