30 CAUSE AND NATURE OF CROWN-GALL 



instances galls from two to four millimeters in diameter were 

 found on the seventeenth day after the inoculation. The evi- 

 dence seems to be conclusive, therefore, that severe root and stem 

 pruning has nothing whatever to do with the development of 

 this disease. When last examined, January i, 1900, two of the 

 inoculated peach seedlings and four of the apricot showed small 

 developing galls. None were found on the walnut, grape, and 

 apple. However, as the latter had made no growth since cut- 

 ing back and replanting, it is possible that galls may develop 

 upon them during the coming summer if they are allowed to 

 remain in the soil. It is likely also that more of the inoculated 

 almond, peach, and apricot trees will contract the disease. 



THE EFFECT OF EXCISION OF THE GALLS AND OF THE 

 APPLICATION OF FUNGICIDES. 



Five almond seedlings with large galls at the crown were 

 treated on November 12, 1899, by carefully removing the galls 

 and placing a quantity of the flowers of sulphur on the wounds. 

 In every instance the galls returned, the sulphur having no 

 apparent effect upon them. On the same date five other 

 almond seedlings were similarly treated, with the exception 

 that the paste of Milestone, copperas, and quicklime was placed 

 on the wounds. Two months later the galls had not reappeared. 

 It is probable that the corrosive action of the mixture prevented 

 the growth of the soft succulent tissue of the gall, and thus 

 checked the development of the organism itself. 



SOME MISCELLANEOUS EXPERIMENTS RELATING TO CROWN- 

 GALL. 



A large number of fungi, mostly, if not entirely,, saprophytic, 

 are nearly always found on the surface or in the outer portion 

 of old galls— sometimes one fungus, sometimes another. Some, 

 however, send their mycelium to some distance into the living 

 hypertrophied tissue. Thinking that possibly one of these 

 might be the cause of the disease, as suggested by the observa- 

 tions of Halsted,' 2fi four of the species (unidentified species of 



26 Bull. Torr. Bot. Club, XXIV, 508. 



