42 



Walter H. Burkholder 



A chlorotic zone is not so evident, although the lack of a halo is due partly 

 to the fact that the whole leaf is somewhat chlorotic. Nevertheless it is 

 very noticeable that a halo spot is never produced in the hot days of July 

 and August. The angular spots just described probably arise from sto- 

 matal infection, and in most cases are an infection of the islets between 

 the veins. 



Other necrotic leaf spots due to this organism may arise, similar in 



Figure 8. primary leaf of a bean plant which was inoculated at the 

 cotyledon node with phytomonas medicaginis var. phaseolicola 



