THE CAUSE OP CROWN-GALL. 21 



knots. Comes (7) in 1891 thought that the disease was caused by 

 Bacterium gummis and also the disease known as gummosis. Trevi- 

 san a named the organism as isolated by Cavara (5) Bacillus ampe- 

 lopsorae n. sp. Cavara (5) claims to have proved the pathogenesis of 

 this organism by inoculation with pure cultures. 



Cooke (9) in 1893 described a disease on the roots of grapes much 

 like the crown-gall. He asserted that he found a species of Plasmo- 

 diophora in the galls. This in 1903 he designated as Plasmodiophora 

 vitis (10). He did not, however, prove the pathogenesis of the organ- 

 ism he found. 



Woodworth (60) mentions the finding of a species of Micrococcus in 

 grape galls which he grew in a pure culture, but he did not prove the 

 pathogenesis of the organism. 



Reddick (41) in 1909 described a fungus Fusicoccum viticolum, 

 which he isolated a number of times from the cane galls of grapevines 

 in New York. He ascribed the disease to this fungus. 



The writer, in July, 1903, in a study of the disease at Bernalillo, 

 N. Mex., found constantly occurring in the tissues of grape, cane, and 

 root galls and in adjacent diseased tissues a motile bacterial species 

 which was isolated repeatedly and grown in pure cultures in poured 

 agar plates and slant agar tubes in a culture medium consisting of 

 a decoction of celery added to McDougal's culture solution. In agar 

 plates the colonies were round, with a smooth edge, whitish in 

 color, and viscid when drawn out with a needle. No inoculations 

 were made with the organism at the time. These cultures were lost 

 in transit to St. Louis, Mo., where they were sent for further study. 



Again, in July, 1904, a number of organisms, including five kinds of 

 bacteria, were isolated from grape root galls. These were grown in 

 pure cultures and inoculated in young Muscat of Alexandria and in 

 Tokay grape seedlings. One of these organisms was in appearance 

 similar to the one found in 1903, and of three Muscat of Alexandria 

 seedlings inoculated with a pure culture of it two became diseased 

 with galls at the point of inoculation. Wounded control plants 

 remained healthy. Although the limited nature of the experiment 

 rendered the results inconclusive, owing to the urgency of the imme- 

 diately practical aspect of these investigations, this work was not 

 prosecuted further at that time. 



In April, 1907, Smith and Townsend (45) of the Bureau of Plant 

 Industry, published an article describing a plant tumor of bacterial 

 origin. They gave conclusive proof of the pathogenesis of the organ- 

 ism Bacterium tumefaciens, n. sp., which was isolated from the galls 

 of the Paris daisy, grown in pure cultures, and studied. This organ- 

 ism, when inoculated into healthy plants of tobacco, tomato, potato, 

 sugar beet, hop, and peach produced galls at the point of inoculation. 



oSaccardo. Sylloge Fungorum, vol. 8, p. 983. 

 183 



