12 CAUSE AND NATURE OF CROWN-GALL 



gious character of the disease, and, in one of his later reports, 2 " 

 writes as follows : 



"Under every condition of soil, climate, and host plant the 

 disease has the same characteristics and to be always and im- 

 mediately distinguished from other forms of hypertrophied plant 

 tissue. This fact is to be explained upon no theory other than 

 that it is caused by the attacks of a particular organism." 



Yates 21 and Lelong are the only experimenters with this dis- 

 ease, of whom I am aware, that conclude that the disease is 

 not a true infection. As Lelong's experiments were not dupli- 

 cated and were not tried under varying conditions, it is very 

 probable that if tried at different seasons and with varying con- 

 ditions they would have shown the communicability of the 

 disease. Yates attempted to communicate the disease by bud- 

 ding and grafting, but without success. From the nature of 

 the disease, this is to be expected. He also attempted to pro- 

 duce the disease by inoculation, but with no better success. 

 His conclusions are somewhat in accord with those of Sorauer 

 in his description of Wurzelkropf in Germany. Bailey 22 is in- 

 clined to accept this statement of the case, and in his account 

 of the disease in New York concludes as follows : 



' ' The conclusion of the whole matter, then, as we now under- 

 stand it, is that these root-galls are not the work of a parasite, 

 but are a malformation following some injury of the root or some 

 uncongenial condition in soil or treatment. The galls may seri- 

 ously interfere with the nutrition of the plant, in many cases 

 causing it to become weak and sickly. It is probable that the 

 trouble is not communicable, and that cutting off the gall averts 

 further trouble from that source. As a precautionary measure, 

 however, we much prefer to plant only trees with perfectly clean 

 and normal roots." • 



GEOGRAPHICAL DISTRIBUTION OF CROWN-GALL IN THE 

 UNITED STATES. 



In the fall of 1897 I addressed the following letter to each of 

 the experiment stations in the United States in order to ascer- 



i0 Rept. Cal. Agr'l Exp. Sta. 1894-95, 231. 



2t Cal. Fruit Grower 1895, ill. 



-Bull. Cornell Agr'l Exp. Sta., 117, 375- 



