Il8 FUNGOUS DISEASES OF PLANTS 



organism grows very slowly at blood heat, but shows some growth 

 at o° C. 



Control. It has been found very difficult effectively to cure 

 trees upon which the gall has appeared. Removal of the gall 

 with the tissues adjacent thereto, and the use of antiseptic 

 washes, do not insure -the complete isolation of the disease. It 

 is evident, therefore, that there is difficulty in removing all dis- 

 eased tissues. Since the gall develops promptly in nursery stock, 

 it is readily detected at the time of transplanting, and such in- 

 fected stock will, wherever possible, be discarded. Any injuries 

 to growing trees at or near the surface of the ground will make 

 infection easier, and consequently care should be taken in the 

 cultivation of orchards. 



V. OLIVE KNOT, OR TUBERCLE-DISEASE OF THE OLIVE 



Pseudomonas Ohm (Arc.) Trev. 



Petri, L. Untersuchungen iiber die Identitat des Rotzbacillus des Oelbaumes. 



Centrbl. f. Bakt., Parask., u. Infektkr. 19 (Abt. II): 531-538. 1907. 

 Pierce, N. B. Tuberculosis of the Olive. Journ. Myc. 6 : 148-153. _^/j. y^- 



15- i 8 9 r - 

 Savastano, L. Tuberculosi, iperplasie e tumori dell' olivo. I e II Memoria, 



Ann. d. R. Scuola Sup. dAgr. in Portici 5 : 131 pp. 1887. 

 Smith, C. O. A Bacterial Disease of Oleander. Bot. Gaz. 42 : 301-310. 1906. 

 Smith, Erw. F. Recent Studies of the Olive-Tubercle Organism. Bureau 



Plant Industry, U. S. Dept. Agl. Built. 131 : 25-43. 1908. 



The olive knot was known in early times. It is not uncom- 

 mon throughout the Mediterranean region, but it is perhaps 

 most abundant in Italy. It seems to occur also in California. 

 The knot is conspicuous from the development upon the smaller 

 twigs and branches of a knob or tuberculate swelling. Small 

 swellings may also occur on the leaves. The formation of the 

 tubercle usually begins in the spring, and where the tubercle 

 surrounds the branch the latter suffers considerable injury, and 

 may eventually die. 



Inoculation experiments made with pure cultures of the iso- 

 lated organism have yielded characteristic infections, both in the 

 experiments reported by Italian investigators and in those of 

 Erwin Smith 1 in the United States. C. O. Smith has studied 



1 Smith, Erwin F. Bacteria in Relation to Elant Diseases 1 : 10. 



