VOL. XVI. NO. 3— BOTANICAL GAZETTE — MAR.'. 1891 



Black rust of cotton: a preliminary note. 1 



GEO. F. ATKINSON. 



Early in the past season I began a study of the fungous dis- 

 eases of the cotton plant with the special object to determine 

 the disease called "black rust." The first of August, 1890, 

 one hundred circular letters were sent to different farmers of 

 Alabama requesting specimens of * l black rust," "red rust," 

 1 * Frenching, " "root rot," etc. As it seemed probable that 

 there was some confusion in the application of these names 

 to certain appearances of the cotton a special request was 

 made of the senders to carefully label the plants with the 

 name applied by them to the disease. 



, From twenty-five to thirty replies were received including 

 specimens marked "black rust," "red rust," and "root rot." 2 



The disease has been very prevalent and destructive during 

 the season and excellent opportunities were afforded me for 

 studying it in the vicinity of Auburn, not only upon the sta- 

 tion farm but on neighboring plantations. 



July 22d, on one of my visits to the cotton field, I found the 

 disease had made its appearance in full force in several spots, 

 where fully one-half of the leaves of the plants had fallen off, 

 the remainder being curled, dried, and blackened by a profuse 

 development of darkhyph«ne and spores of several fungi, so that 

 by suddenly jarring a leaf the spores would float off in clouds 

 like the smut spores of some of the Ustilagineae. Some of 

 the plants showed still the earlier stages of the disease, and 

 in other parts of the field were numerous opportunities to 

 study the earlier stages. For two months my time was occu- 

 pied in noting the external characters, collecting material, ex- 

 amining the different fungi found and noting the relation of 

 each species to the variety of external characters presented 

 in the progress of the disease. 



1 Paper read before the American Association of Agricultural Colleges and 

 Experiment Stations, Champaign, III., Nov., 1890. 



2 The "root rot" disease was reported from only one place. The effects of the 

 disease upon the plant are strikingly similar to those produced by the Texas dis- 

 ease which is caused by Ozonium according to Pammel, but due to an entirely 

 different organism, a nematode worm, Heterodera radi cicala. 



