EXPERIMENTS WITH THE POPLAR ORGANISM. 93 



POPLAR ON APPLE. 



Inoculations of July 20, 1910 (Smith and Brown). 



Six slioots were inoculated by needle pricl^ from an agar streak 

 culture 5 days old. 



Result. — All grew well. One yielded in the pricked spot a distinct, 

 rounded, corky tumor one-fourth inch in diameter. The other 5 

 failed. 



POPLAR ON BRASSICA. 

 Inoculations ok July 20, 1910 (Smith). 



The organism derived from the Flats poplar was inoculated by 

 needle pricks into growing stems, using a peptone water culture 5 

 days old: (1) Early Summer cabbage; (2) Early Wakefield cabbage; 

 (3) coUard; (4) Tall Green Scotch kale; (5) kohl-rabi. 



Result. — October 21, 1910: (1) The four inoculated plants bear 

 galls in the pricked area and not elsewhere. On one they are small; 

 on the others they are 1 to 2 inches in diameter (PI. XXXIII, fig. B). 

 Eleven uninoculated plants in the same pots are free. (2) Two 

 plants bear largo galls (1 to 2 inches in diameter), but only in the 

 pricked areas; 6 checks are free. (3) One large coliard bears a 

 dozen small knots (one-fourth to one-half inch in diameter) in 

 ])ricked area and not elsev*diere. One-half of one knot shows hairy- 

 root (PI. XXXIII, fig. A). No other collards. Cabbage checlcs 

 free. (4) One plant has 2 well-defmed small galls (one-fourth inch) 

 in pricked area and none elsewhere. Eight checks free. (5) Top 

 of inoculated plant missing, i. e., broken off by someone (this was 

 the pricked part); 10 checks free. These stood close to the Wake- 

 field cabbage and the kale. 



POPLAR ON SUGAR BEET. 

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



In May, 1910, an organism resembhng Bacterium tumefaciens was 

 plated from a gall on Populus deltoides (called "Flats poplar" be- 

 cause the tree stands on the Flats near the river below the Washington 

 Monument in the District of Columbia). These galls grew in clusters 

 on the extreme base of the trunk of a large tree, but were not large; 

 i. e., only 1 to 3 inches in diameter. 



The material used for inoculation was an agar streak subculture 

 (Ma}^ 31) from a poured-plate colony. Ten sugar beets in a row 

 were inoculated on the root toward the crown by needle pricks. 



Result. — July 5, 1910: 100 per cent of infections. Galls began to 

 develop at once in the pricked parts, but the plants v/ere allowed to 



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