140 ANNALS OF THE MISSOURI BOTANICAL GARDEN 



[Vol. 10 



determined. As in the case of other plant parasites, entrance 

 may be effected through wounds produced by insects, such as 

 leaf-hoppers and flea-beetles, which puncture the epidermis 

 in their feeding operations. It would seem, however, judging 

 from the general infection of many plants, that the fungus is 

 not dependent entirely on wounds for access to the host tissues. 

 Stomata present on pods and leaves doubtless serve as places of 

 entrance. Moreover, the hyphae may be able to penetrate the 

 unbroken epidermis. It has not been possible to date to deter- 

 mine this point with certainty. 



The difficulty of obtaining infections under dry conditions 

 when spores are atomized on pods and stem would indicate that 

 entrance is mainly through the stomata. Infections are readily 

 obtained by this method when plants are maintained in a highly 

 humid atmosphere, possibly because stomata are usually open 

 when light and atmospheric moisture are abundant. 



Infection is first made evident on pods by the appearance of 

 a darkened, water-soaked area about the point of inoculation 

 or by a premature yellowing and browning of infected tissue. 

 Pycnidia may or may not appear on the surface. Even when 

 pycnidia do not develop on diseased pods in the open, the ovules 

 or seeds may be found covered with a conspicuous weft of hyphae, 

 and the characteristic fruiting bodies of the fungus develop 

 when such pods are placed in moist chambers. If pods become 

 infected when less than about one-fourth grown, the ovules 

 commonly fail to develop further and the pods fall from the 

 plant. Older pods usually cling firmly to the stems bearing 

 them. 



Overwintering and Dissemination 



The soybean pod-blight organism passes the winter on dead 

 stems and pods and in diseased seed. Dead stems bearing 

 numerous pycnidia were collected in the fall and wintered out 

 of doors on the ground. Pycnospores were present in a part 

 of the pycnidia on May 5 of the ensuing year and these showed 

 abundant germination in tap water at room temperature. 

 Stems similar to those described above were wintered in an open 

 can in the laboratory. On May 18 spores from these stems 



