1923] 



DUGGAR & KARRER — NATURE OF MOSAIC DISEASE PARTICLES 197 



demonstration of a plasma-like body, but whether or not it may- 

 be a modified cell structure, a pathological by-product, a colony 

 of granular bodies, or something else, is not yet clear, nor is its 

 significance in relation to the "mosaic" disease of these mono- 

 cotyledons known. 



A study of tobacco mosaic in Sumatra by Palm ('22) brings 

 casual reference to some abnormal structures. He refers very 

 briefly to cytological work on this mosaic and mentions the occur- 

 rence of corpuscular bodies more opaque than the general proto- 

 plasm. Likewise, he notes the occurrence of "a second foreign 

 cell element, consisting of extraordinary, small granules." With 

 this hazy evidence he proceeds to relate the bodies to the "so- 

 called corpuscles of Gardner" and concludes that a "Strongylo- 

 plasma" species must be considered as the cause of the disease. 

 Indeed, he designates the "organism" Strongyloplasma Iwanow- 

 skii, promising a more extended publication. 



The sensation of the joint meeting of the Botanical Society of 

 America and the American Phytopathological Society at Boston 

 in December, 1922, was a report by Nelson on "The Occurrence 

 of Protozoa in Plants Affected with Mosaic and Related Diseases." 

 The stage was well set for such an announcement. The titles of 

 several papers arranged for that same meeting indicated the 

 finding of unusual structures in the cells of several plants affected 

 with mosaic-like diseases. The careful work of Kunkel ('21, '22) 

 referred to earlier in this paper; the observations of Matz ( , 19), 

 Palm ('22), and Dickson ('22); the attention recently bestowed 

 upon the existence in the spurge and milkweed families (Lafont, 

 '10; Franca, '20; and Mesnil, '21) and other dicotyledons 

 (Franchini, '22, '22 a-g) of flagellates normal to the latex tubes, 

 these considerations all served to establish an atmosphere on that 

 stage exceedingly favorable or impressionable in respect to 

 protozoology. Under such conditions Nelson described or pre- 

 sented upon the screen in the form of photomicrographs evidence 

 for the existence in bean mosaic of 6 principal forms or types of a 

 protozoan organism alleged to occur in the phloem of a diseased 

 plant. It is impracticable here to take the time to indicate the 

 characteristics of most of these types of flagellates described. 

 The paper has since appeared as a technical bulletin of the 



