Bean Anthracnose 121 



spore, and in the writer's cultures this condition was frequently met. 

 Atkinson found that the ends of the hyphal threads have a dichotomous 

 appearance, due to a branch just behind the growing end overtaking 

 the primary thread, and that a plumose tuft is produced by this dichoto- 

 mous branching taking place successively in the same thread. 



The mycelium, which at first is white, will become dark-colored after 

 a growth of several days in a starch-containing medium. This is especially 

 noticeable with the growth in potato agar and bean, agar and on sterilized 

 bean pods. A culture four or five days old shows a dark center with 

 pure white mycelial growth at the margin and aerial mycelium developing 

 over the surface. As growth continues, dark-colored knots of mycelial 

 threads appear scattered from the center outward, and above these darker 

 parts of the culture, flesh-colored masses of spores (acervuli) begin to 

 be produced if the culture is in good condition. Dey (1919) finds that 

 in cornmeal agar cultures these spores are surrounded by small dark 

 spines. On sterilized bean pods inoculated with spores kept at a tem- 

 perature of about 22° C, there is a rapid growth of mycelium which in 

 two days begins to darken and after three days produces spores in acervuli . 

 In six days the pod is covered with a pale salmon or pale flesh-colored 

 mass of spores. Cultures kept for a long time or at unfavorably high 

 temperatures lose their power to develop spores in this way when trans- 

 ferred to fresh media. Commonly they develop only a slow growth of 

 white mycelium. Spores will usually be produced if the mycelium turns 

 dark. 



Viala and Pacottet (1905), from a study of Colletotrichum linde- 

 muthianum in culture, report the production of spermagonia, pycnidia, 

 cysts, yeasts, and sclerotia, as well as conidiophores, similar in most 

 respects to those produced by Manginia ampelina, another fungus under 

 their observation. Shear and Wood (1913:64) say yeasts have never 

 occurred in their cultures of Gloeosporia except where they were evidently 

 contaminations, and they have never observed the production of sper- 

 magonia or pycnidia by these fungi. No other writers in speaking of 

 C. lindemuthianum or related forms have mentioned the production of 

 bodies of these kinds, except that Edgerton (1910:10) reports having 

 once found pycnidia-like bodies in the tissue of the bean seed. 



Temperature is an important factor in the development of the fungus 

 in connection with its host or in culture media. Edgerton (1910:29) 



