Histologic changes induced by certain phytopathogens.

The histologic features of the following diseases have been studied: (1) Delphinium Black Spot, caused by Bacterium delphini (E.F.Smith) Bryan. (2) Cauliflower Leaf Spot, caused by Bacterium maculicola (McC.) McCulloch. (3) Black Rot of Crucifers, caused by Bacterium campestre (Pam.) E.F.S. (4) Fireblight of Apples and Pears, caused by Bacillus amylovorus (Burrill) Trevisan. (5) Bacterial Blight of Bean, caused by Bacterium phaseoli E.F.Smith. (6) Beet Leaf Spot, caused by Cercospora beticola Sacc. The most important findings were in connection with cicatrice formation. In (2) and (6) active disease resistance responses, including occlusion of the intercellular spaces and, under warm Bonditions, the formation of wound cork round the lesions, were observed. In the remaining diseases active resistance responses were not noted except in a few cases which appeared to be abnormal. Wounding tests on leaves of cauliflower, turnip, cabbage, bean and beet indicated their ability to form wound cork similar to that formed round disease lesions. [...