THE ANGULAR LEAF-SPOT OF COTTON: TYPE 



319 



East Africa (Nyassaland), and more recently (1915) from cotton 

 grown in Pretoria in S. Africa. In 1915, Bovell and Dash re- 

 ported it as serious on late cottons in the Barbados. In 1918 

 Reinking reported it from the Philippines. Miss Doidge writes 

 me (1919) that she has observed it to be quite common in South 

 Africa. O. F. Cook saw it in China in 1919. Probably the 

 disease occurs in all the cotton-growing regions of the world. 



Fig. 242. — Inoculated cotton leaves showing angular spots duetto stomatal 

 infection by Bacterium malvacearum. Bacterial suspension sprayed on. Spots 

 in second stage, i.e., beginning to shrivel and brown. Time, 6 weeks. Photo- 

 graphed April 28, 1915. >2 nat. size. 



The extent of damage done by it is unknown. It is worse 

 in some localities and some seasons than in others. I regard 

 it as a serious disease. 



If any considerable part of the ''shedding" of the young 

 bolls is due to it, especially in seasons when shedding is phe- 



1. Result of inoculating cotton leaves when very young. Stomata not then 

 open on the parenchyma and attack of Bacterium malvacearum confined chiefly 

 to the veins: a, bacteria rubbed by hand on under-surface of right lobe; b, 

 bacteria sprayed on. Photographed April 28, 1915. Time: a, 4 weeks; b, 6 

 weeks. 



2. a, Hand-rubbed (March 25) with Bacterium malnacearum on the under- 

 surface of the right lobe when very small and infection confined to the vicinity 

 of veins; 6, sprayed when older (March 17), i.e., when about half-grown and 

 disease confined to the parenchyma. Photographed May 1, 1915. 



