EdGERTON : BOTRYOSPHAERIA ON COTTON BOLLS 35 



ascogenous stage. The pycnidial stage occurs during the summer 

 and is followed by the ascogenous stage in the fall. A boll 

 affected by this fungus turns black, dries up, and becomes cov- 

 ered with the fruiting stages. 



The pycnidia develop profusely on the surface of the diseased 

 boll, usually almost superficial, though sometimes they may have 

 the base slightly surrounded by fungous or host tissue. They are 

 black in color and about 110-300 X 140-210 /a in size. The 

 spores are developed abundantly on short conidiophores and are 

 pushed out of the pore at the apex of the pycnidium. If weather 

 conditions are favorable, these spores remain in white strings 

 protruding from the pycnidia. The spores are hyaline, one-celled, 

 from cylindric to slightly elHpsoid or ovoid, coarsely granular, 

 and 14-33 X 7-10 /X in size, averaging about 21-25 X 8 /x. The 

 spores are never septate nor dark-colored and are much more 

 variable in shape and size than those of Diplodia gossypina. 



The perithecia are borne in a way similar to the pycnidia and 

 are quite similar in appearance. They are black in color and are 

 about 190-360 X 250-320 /X in size. A short beak may be present 

 or lacking; if present, it may have a length up to 100 /x. The asci 

 are fairly abundant in the perithecia, though not crowded. They 

 are large, about 100-130 X 20-25 /x, and have very thick walls, 

 especially near the apex. The ascospores are hyaline, ellipsoid, 

 slightly granular, and about 20-27 X 10-16 /x in size. The small 

 threadlike paraphyses are very abundant. 



The fungus has been cultured a number of times both from the 

 conidia and the ascospores. A good growth develops on most of 

 the ordinary culture media but as yet no spores of any kind have 

 been produced in culture media. 



To prove the identity of the two forms, inoculation experi- 

 ments were tried. In the winter of 1909-10, a pure culture was 

 obtained from conidia, and this was used during the summer of 

 1910 to inoculate a number of bolls in the field. The fungus is 

 not a very active parasite under field conditions, so only a part of 

 the bolls became affected. These, however, on which the inocu- 

 lation was successful, developed the pycnidia abundantly and 

 later in the season some of them developed perithecia and asco- 

 spores. Single asci were then transferred to acidified culture 



