CAUSE AND NATURE OF CROWN-GALL 



31 



Torula, Polyporus, Chalara, and Pythium?) most frequently 

 found associated with the gall were grown as pure cultures on 

 sterilized pieces of boiled potato and the cultures used in inocu- 

 lating almond seedlings. Twelve seedlings growing in the 

 open were inoculated with these cultures, three seedlings being 

 inoculated with each culture. In not a single instance were 

 galls obtained during the period of observation, which covered 

 nine months. In some instances, however, there was consider- 

 able decay at the places where 

 the incisions were made, but 

 no hypertrophied tissue devel- 

 oped. 



Nematode worms are fre- 

 quently found associated with 

 the old galls. This is particu- 

 larly true of seedlings grown 

 in the green-house and sub- 

 ject to overwatering. As it 

 has been suggested by Selby " 

 that these worms possibly ac- 

 count for the disease, a careful 

 study was made of the species 

 found associated with the gall 

 in order to ascertain, if possi- 

 ble, their relations to it. At 

 least three species were found. 

 Two of these were undoubt- 

 edly free-living nematodes, one of which agrees with a free- 

 living Rhabdites figured and described by Stone and Smith. 28 



A number of these worms were separated from the partially 

 decayed tissue forming the outer portion of the gall, washed 

 through several changes of distilled water, and transferred to 

 a piece of partially decayed wood. The wood was placed in a 

 pot containing several small almond seedlings growing in 

 crushed quartz. Two months later no galls were found upon 



Fig. io. -Characteristic galls produced 

 on the roots of an almond seedling by the 

 action of the common gall-forming nema- 

 tode worm. 



27 Rept. Ohio State Hort. Soc, 29, 75 ; Bulls. Ohio Agr'l Exp. Sta., 79, 

 112 ; 92, 214. 



28 Bull. Mass. Agr'l Exp. Sta., 55, 16. 



