52 MISSOURI BOTANICAL GARDEN BULLETIN 
during winter. The galls varied from one centimeter 
in diameter, green and spongy, to several centimeters in 
diameter, brown, corky, and hard, in the older specimens. 
After a continuous study of more than two years with more 
or less negative results, two distinct organisms were isolated 
and later inoculated into young marguerite plants. Numer- 
ous carefully conducted experiments led to the conclusion 
that one of these organisms (Bacterium tumefaciens Smith 
and Townsend) was responsible for the abnormal growths. 
Cross inoculations firmly established this point and indicated 
that the pest varied in its adaptability and virulence in dif- 
ferent hosts. 
The following table illustrates the appearance of the or- 
ganism upon different plants subject to its attack and the 
widespread occurrence of the disease: 
PLANT DESCRIPTION OF TUMORS 
Marguerite 
Chrysanthemum Leaves yellowed at edges; galls on stems green, 
Marigold later corky, brown 
English daisy 
eras Slow-growing, hard tumors 
Tobacco Knots 4 inch in diameter formed all over the 
plant 
Beet 
Radish Large irregular tumors on the side of the roots 
Carrot 
Grape Galls on underground as well as aérial parts 
Peach Galls 1-2 inches in diameter occurring at the 
Almond crown or just below it 
rt aad Galls at crown 
Quince _ | Warty galls on stems, entire limbs often being 
covered with irregular outgrowths 
come 
Blackberry 
Sil-aineer _ | Galls upon roots 
Alfalfa 
Rose Large galls at crown and roots 
Geranium ~ tage galls, upon stems at nodes, covered with 
Castor bean abortive leafy shoots 
Shrubs and trees, 
particularly 
Populus alba, 
Castanea dentata, Crown galls 
Juglans niger, and 
Salia 
