92 CROWN-GALL OF PLANTS. 



pricks failed. (2) Four rounded tumors, largest one-half inch; sev- 

 eral pricks failed. (3) Missmg. (4) Three very small laiots (one- 

 sixteenth to one-eighth inch) ; rest of pricks failed. (5) Six small 

 rough galls, each about one-eighth inch in diameter, 5 on stem, 1 on 

 petiole; 10 pricks failed. (6) Six small rounded tumors (one-eighth 

 to oiie-quarter inch). 



POPLAR ON OPUNTIA. 



Inoculations of July 5, 1910 (Smith and Brown). 



Growing branches were inoculated by needle pricks from an agar 

 streak culture 4 days old. Four varieties were used, having the 

 followuig appearance, viz: (a) Elongated, dark-green joints, which 

 are uniformly fine-hairy, and nearly free from prickles, i. e., short, 

 weak spines; (b) smooth, light-green, elliptical, or pear-shaped, thin 

 joints, with inch-long, smgle spines; (c) like h but v/ith clusters of 

 spines; (d) somewhat like h, but with round flat branches, very long 

 spines, and clusters of brownish short prickles. 



Result. — October 21, 1910: (a) Negative, one shoot inoculated; 

 (b) one of the two pricked joints has, where inoculated, a smooth 

 round tumor half an inch in diameter; (c) two young shoots, negative; 

 (d) two shoots, negative. 



December 19, 1910: The tumor on h is smaller than it was, and 

 nipple-like projections have appeared on it. 



February 8, 1911 : The tumor has not increased in size. 



POPLAR ON COTTON. 



Inoculations of July 20, 1910 (Brown). 



Inoculated the crowns of 6 3"oung growing cotton plants (Willet's 

 Red Leaf), with a 5-day-old 2 per cent peptone water culture of 

 Flats poplar gall organism. (For origin see "Poplar on sugar beet/' 

 p. 93.) Held 2 checks. 



Result. — October 21, 1910: iVll negative. The plants grew well. 



POPLAR ON GRAPE. 



Inoculations of June 4, 1910 (Smith and Brown). 



Two small shoots of Vitis vinifera were inoculated in the green 

 terminal growing parts by needle pricks -with an agar subculture 

 from a colony derived by poured plate from a gall found on the 

 trunk of a large tree of Populus deltoides (P. monilifera) in Washing- 

 ton (Flats below the Washington Monument). 



Result. — July 18, 1910: One of the inoculated shoots bears a 

 dozen small tumors, and the other 26 (PI. XXIV, C). There are 

 no galls on the plants except where they were pricked. 



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