GALLS AND TUMORS. 503 



just below the ground line (crown), at or near the juncture of the stock 

 and scion in grafted plants. Ordinarily, they are smooth, soft, spongy, 

 white to flesh- colored outgrowths which increase in size, harden and be- 

 come rough and warty on the surface with age. As the galls* enlarge, 

 the function of the adjacent conducting tissue is interfered with, and the 

 circulation is impaired, as is shown by the poor growth and dwarfed 

 appearance of the trees. Secondary galls often appear on the smaller 

 roots and less frequently on the structure above ground. 



The disease is a communicable one and is cross inoculable on culti- 

 vated plants to an astonishing degree. 



METHOD OF INFECTION. Little is known about the natural channels 

 of infection, but inoculation through wounds, induced by grafting and by 

 careless cultivation, is undoubtedly responsible for many crown galls. 



CAUSAL ORGANISM. According to Smith and Townsend,"}" Bact. tumefaciens is a 

 short rod with rounded ends, motile by 1-3 polar flagella. On agar and potato, growth 

 viscid, white. Broth, surface ring. Blues litmus milk and precipitates casein with 

 reduction of litmus. Gelatin not liquefied. No growth in Cohn's solution. No gas 

 formation. Aerobic. Does not grow at 37. Best isolated from that part of the stem 

 where the tumor joins the healthy tissue. 



CONTROL. Thorough inspection of nursery stock, and care in the 

 cultivation of orchards not to wound the crowns are important factors. 

 Removing the galls results in no practical benefit. 



OLIVE KNOT. 



Bacterium savastanoi Smith. f 



The olive knot 'has been known for many years, and is even described 

 by the early Roman writers; its bacterial nature, however, has been 

 recognized only since 1886. It is most prevalent in those countries which 

 border on the Mediterranean Sea, but it also occurs in the olive growing 

 sections of California. 



* Very hairy roots often accompany these. 



f Smith, Erw. F. and Townsend, C. O.: " A Plant Tumor of Bacterial Origin," Science, N. S. 

 Vol. XXV, 643, p. 671-673, 1907. "The Etiology of Plant Tumors." Science, N. S. Vol. XXX., 

 763, p. 233, 1909. 



f Townsend, C. O. " A Bacterial Gall of the Daisy and Its Relation to Gall Formations on 

 Other Plants, Science, N. S. (Abstract) Vol. XXIX., p. 273: 1909. 



J Savastano, L. Les maladies de 1'olivier et la tuberculose en particulier. Comp. Rend. 103 

 1144, 1116. II baccillo della tuberculosi dell'olivo, nota suppletiva. Rend. Lincei 5: 92-94. 

 1889. 



t Smith, Erw., Bull. 131, Part IV, Bur. of Plant Industry, U. S. Dept. of Agriculture, 1908. 



