EXPERIMENTS WITH THE HAIEY-EOOT ORGANISM. 103 



HAIRY-ROOT ON YOUNG APPLE TREES. 

 Inoculations of April 5, 1909 (Brown). 



Twelve young apple trees entirely free from gall or hairy-root were 

 washed carefully and 8 of them inoculated with 2-day-old agar cul- 

 tures of the apple hairy-root organism (Whetzel tree). Twenty-live 

 pricks in groups of 5 were given each root, beginning at the crown and 

 going down. The stem was notched to indicate the side inoculated. 

 Four checks were held, the punctures being made in the same way. 



Result. — -May 3, 1909: Turned back the soil, examined, and found 

 tliat hau's were forming in the })ricked places. 



September 3, 1909: Dug the trees, washed, and examined them. 

 Five of the 8 showed very good cases of hairy-root (PL XVIII, figs. 

 1 and 2). Two failed and one bore rather small hard galls without 

 hairy-root. One of the checks also had several small galls. This 

 tree must have become infected during the planting. Plates were 

 made from one of the hard gaUs obtained from the inoculated tree 

 which did not bear hairy roots and an organism isolated. This was 

 successfully inoculated into sugar beets on November 11, 1909, both 

 galls and hairy roots developing. This indicates that the apple gall 

 WSLS actually due to the hairy-root organism, as suspected. 



HAIRY-ROOT ON QUINCE TREES. 

 Inoculations of May 21, 1909 (Brown). 



Three quince trees v^'ere inoculated with a 2-day-old agar culture 

 of the apple hauy-root organism. The trees v/ere in the green- 

 house and just starting to bud out. The wood Avas very tough, 

 but the stems were inoculated at the nodes ami internodes; at 

 least 30 punctures were made on each stem. 



Result. — September 3, 1909: Negative. 



November 28, 1910: (A) Three galls bearing hairy-root (PI. 

 XXXIII, fig. D) on stem well aboveground; (B) one stem gall, 

 no roots from it; (C) several small galls on stem, one bearing hairy 

 roots. 



Five checks on the same bench remained free; also 10 plants of 

 same lot inoculated %vith the organism marked "Quince.'' 



HAIRY-ROOT ON SUGAR BEET. 

 Inoculations of November 13, 1908 (Brown). 



Six young sugar beets growing in an open bed in the greenhouse 

 were inoculated just belovr the surface of the ground, care being 

 taken not to puncture along the line of the root hairs. The inocula- 

 tions were made with agar-plate colonies of the apple hauy-root 

 organism 2 days old. One daisy plant was also inoculated. 



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