[Vol. 10 



114 ANNALS OF THE MISSOURI BOTANICAL GARDEN 



pods — up to one-fourth grown — become infected, they usually 

 fall from the plant, while older pods, in which attachment to 

 the stem had become secure before infection occurred, are not 

 shed. Incipient infections sometimes occur which fail to cause 

 general invasion of the pod tissues. Such limited infections 

 are indicated by small brown areas on the pod wall. 



On stems. — The disease may be found on any part of the 

 stem and branches. Indeed, the pyenidia often appear on these 

 parts when they are not to be found on the pods. No definite 

 lesions, such as characterize diseases produced by other para- 

 sites, are associated with this disease. The mycelium effects 

 a general invasion of the thin-walled portion of the cortex and 

 later enters the stolar tissues, becoming conspicuous in cross- 

 sections of tracheae and pith. After the stem has died or become 

 moribund, pyenidia form in great numbers under favorable 

 conditions (pi. 11, fig. IB) and are often arranged in rather 

 definite lines extending up and down the stems. Thas linear 

 arrangement apparently is dependent upon the tendency of the 

 invading organism to grow in the thin-walled chlorenchyma, 

 lying between the more resistant strands of sclerenchyma of 

 the cortex. In wet seasons pyenidia usually appear simul- 

 taneously over the entire plant, but in such hot dry seasons as 

 that of 1921 they are usually to be found only on a limited 

 area near the ground. Here requisite moisture for infection 

 and subsequent development is available. 



On lea res. —The pod- and stem-blight organism has been found 

 on leaves on only two occasions — once in greenhouse inoculation 

 tests and once in the field. In both instances the type of in- 

 fection was the same. The fungus is not an active leaf parasite 

 and does not produce the definite spotting such as characterizes 



eases due 

 luminous 



pod and stem blight 



of soyb 



but not invariably 



at the tip or margin of the leaflets and steadily progresses back- 

 ward from the tip and inward toward the midrib from the margin 

 until the entire leaflet has succumbed, the veins apparently 

 slightly retarding, but not effectually preventing, the advance 

 of the fungus. Invaded laminar tissue loses its characteristic 



