16T Eleventh Annual Report. 



DEPARTMENT OF BOTANY, 



CROWNGAtL. 



The results accomplished in the investigations that have bee a 

 under way during the past year have been of a very satisfactory 

 nature. The year has been marked by the appearance of Prof 

 Tourney's bulletin containing the complete report of his investi- 

 gations upon the crown-gall, so destructive to fruit trees in Ari- 

 zona. This subject has been under consideration for several years 

 and the ultimate disposition of it as related and illustrated in Bul- 

 letin No, 33 of this Station is matter for congratulation to fruit 

 growers throughout the United- States. 



A brief account of the observations made upon the crown- 

 gall was published in the annual report of a year ago, including 

 greenhouse experiments upon seedlings grown in sterile soil and 

 inoculated with the disease, and upon seedlings springing up 

 spontaneously in an almond orchard at Glendale. These experi- 

 ments proved conclusively the communicability of the disease by 

 contagion and the effectiveness of Bordeaux mixture in checking 

 or preventing it when properly applied. But the discovery of the 

 true cause of the disease was reserved for the investigations of the 

 past winter and the results obtained have been gratifying in the 

 extreme. It was found that the meristematic cells of the gall are 

 filled with the substance of a very delicate parasitic organism, ex- 

 tremely difficult of detection owing to its great similarity, when 

 in the active stage, to the natural protoplasm of the host plant. 

 Organic bodies of this character are known as plasmodia and are 

 not usually parasitic, the only other well authenticated case being 

 that of Plasmodiophora which produces the club-root of cabbage 

 and other Cruciferous plants, Prof. Toumey has been able to fol- 

 low the organism throughout its life-history, to observe the form- 

 ation of the fruit, the production of the spores and to demonstrate 

 their inoculating power. It has thus been shown what extreme 

 care is essential to the prevention of the introduction and spread 



