20 FIELD STUDIES OF THE CROWN-GALL OF THE GEAPE. 



Of the hybrids of Vitis cliampini X {labrusca X): Chambrill. Of 

 (Vitis labrusca X vinifera) X aestivalis: Lindherbe. Of Vitis vul- 

 pina X labrusca: Ironclad and Taylor. Of Vitis vulpina x aesti- 

 valis: Bell. Of Vitis vulpina X munsoniana: El vie and. Of ( Vitis vul- 

 pini X labrusca) x vinifera: Rommell. Of Vitis labrusca X :, Moores 

 Diamond, Peter Wylie, and Early Ohio. 



Through the courtesy of Dr. Husmann, the writer was permitted 

 to take notes on a large number of vines being tested by him in sev- 

 eral localities in California for resistance to phylloxera and alkali. 

 Through observations made in these and other vineyards in Cali- 

 fornia, where vines are being grafted and grown on resistant stocks, 

 it has been noted that where varieties like the Muscat of Alexandria, 

 Mission, and others susceptible to crown-gall are grafted in stocks 

 resistant to phylloxera there is often acquired a resistance to crown- 

 gall. 



A number of vineyards were examined in central and southern 

 California in which the vines were grafted on Rupestris St. George 

 and Lenoir and other stocks resistant to phylloxera. These were 

 found to be almost free from crown-gall. Neighboring vineyards 

 of the same age where the vines were grown on their own roots were 

 found to be very considerably or even badly diseased. This gives 

 still greater importance to the need of obtaining resistance by graft- 

 ing in resistant stocks. 



THE CAUSE OF CROWN-GALL. 



The earlier investigators of crown-gall mistook the conditions of 

 environment which favor the disease for its cause. The greater 

 number of European observers have assigned the cause of the disease 

 to physical agents, such as late frosts and winter killing. Among 

 those who ascribed the cause of cane galls (Grind, broussin, etc.) pri- 

 marily to injury received from freezing are Dornfield (15), Kohler 

 (33), Du Breuil (16), Beinling (2), Goethe (28), Viala (55), Frank 

 (21), and Sorauer (48). 



Garovaglio and Cattaneo (23) and Dehors (13) thought that the 

 disease might be brought about by injuries received from insects. In 

 addition to the action of frost and injuries by insects, some investi- 

 gators, according to these writers, have advanced the opinion that a 

 superabundance of the food supply might favor the disease. 



Von Thumen (58) found a species of Fusisporium in the galls and 

 ascribed the disease to the action of the fungus, but did not prove its 

 pathogenesis. 



Corvo (11) in 1885 noted the presence of bacteria in the tubercles, 

 or galls, on grapevines. Cuboni (12) in 1889 observed bacterial 

 zooglcese in such galls and compared them with the bacteria in olive 



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