Stupii-s on Crown C.ai i or Pi ants 429 



specimens of crown i^all of the }X'ach. but only for plasmodia or 

 funi;i as parasitic causes of the mahidy. Since tlien, other able 

 scientists, among them, X^'aite, von Schrenk, P. J. O'Gara, and 

 George Grant Hedgcock, had made some study of the disease 

 but never discovered its cause. Hedgcock was a graduate of the 

 University of Nebraska and since 1901 had been with the Depart- 

 ment in several capacities as a plant and forest pathologist. 



Tourney's " Inquiry into the Cause and Nature of Crown-Gall " " 

 had been principally concerned with the disease as found in 

 almond trees, and its causal organism, he believed, was myxomy- 

 cetous in nature. Dendrophagus had been chosen for the name 

 of his proposed new genus "' to suggest the cancerous character 

 of the gall tissue," and globosus was suggested for the species 

 because of " the form of the mature sporangium." He regarded it 

 as " a specific organism, belonging to the slime-molds, or Myxo- 

 mycetes. Altogether," he said, 



about 200 species of slime-molds have been published as occurring in 

 North America. Of this large number but a single species is known to be 

 parasitic, and this is considered by some authors as a doubtful Myxomycete. 

 The parasitic species heretofore described is the common Plasuiodiophora 

 briusicae, which causes the disease known as "' club-root " in cabbage and 

 allied plants. 



Smith had " never seen anything on or in crown galls which 

 ha[d] in any way led him to think that Myxomycetes have any- 

 thing to do with their production. Phenomena," he wrote in 

 1911,'*^ " similar to that described by Toumey were seen inde- 

 pendently by the writer as long ago as 1893 in cells of the crown 

 gall of the peach, and after six months' work upon the subject, 

 the conclusion was reached that the appearances were artefacts 

 and not living slime molds." He had seen and studied Toumey's 

 slides, but had never been convinced that the organism described 

 and figured by him " had any connection whatsoever with the cell- 

 changes in the gall also described and figured by him. . . . But 

 even granting Toumey's interpretation as correct," he wrote 

 further, 



*^ op. cii., Bulletin 33, April 13, 1900, publ. of Univ. of Arizona Agric. Exp't 

 Sta., 64 pp. See pp. 14, 21, 25, 26, 39, 55. 



"E. F. Smith, Crown gall of plants. Phytopathology 1(1): 7-11, Feb. 1911; 

 quotation taken from concluding note, pp. 10-11, at p. 11. 



