52 CROWN-GALL OF PLANTS. 



One daisy plant was inoculated in 4 places from each of the 4 

 tubes used as a check on their virulence. 



Result. — June 1, 1908: Evidence of tumors on 1 shoot (Z) at the 

 place where the punctures were made. The daisy is developing 

 tumors. 



Inoculations of June 9, 1908 (Smith). 



The inoculations were made on branches of 2 potted plants of 

 Populus canescens several feet from the ground with 4-day-old 

 agar cultures of the daisy organism. 



Result. — November 16, 1908: Five small tumors have residted; the 

 largest is about 1 centimeter in diameter. This indicates clearly that 

 gray poplar is also susceptible to the disease. 



December 24, 1908: Branches were photographed (PL V, fig. 2). 



DAISY ON LOMBARDY POPLAR. 



Inoculations op April 17, 1907 (Smith). 



Six trees of Lombardy poplar (Populus fastigiata) were inoculated 

 with 5-day-old cultures, each receiving 30 pricks in groups of 5. 

 Foiu- trees were held as checks. The roots of all the trees were 

 washed thoroughly in the laboratory before inoculating, and the 

 trees were then planted in the greenhouse. 



Result. — July 13, 1907: No tumors resulted from these inocula- 

 tions. The areas punctured by the needle were still plainly visible 

 on the yellow bark of the roots as little black patches. 



Inoculations op May 26, 1908 (Smith). 



Three shoots of Populus fastigiata were inoculated (soft wood near 

 the growing tip) with daisy organism from agar streak 4 days old. 



Result. — June 1, 1908: Nothing definite. 



November 16, 1908: No tumors have resulted. It is difficult to 

 find where the needle entered. So far as these experiments go they 

 tend to show that the Lombardy poplar is not susceptible to this dis- 

 ease, but not enough tests have been made. 



DAISY ON COTTONWOOD. 



Inoculations op April 17, 1907 (Smith). 



Six trees of Populus deltoides were inoculated with 5-day-ol(l 

 cultures, each receiving 30 pricks in groups of 5. Four trees were 

 held as checks. The roots of all the trees were washed thoroughly 

 in the laboratory before inoculating, and the trees were then planted 

 in the greenhouse. 



Result. — July 13, 1907: No tumors have resulted from these inocu- 

 lations, probably because the trees were too old to stand transplanting 



213 



