126 ANNALS OF THE MISSOURI BOTANICAL GARDEN 



[Vol. 10 



on host tissue. Harter ('13) obtained the ascogenous stage of 

 Diaporthe batatatis, a fungus causing a dry rot of sweet potatoes, 

 in cultures isolated from diseased roots. No one has yet reported 

 the finding of perithecia of this fungus on the host. 



No reference has been found in available literature to any 

 disease of soybeans agreeing in etiology and pathological symp- 

 toms with the one herein described. In 1900 Massalongo ('00) 

 published an account of a leaf spot of Soja hispida caused by 

 Phylloslicta sojaecola in Italy. The Soja hispida to which he 

 referred is probably Soja max, but the causal fungi and the 

 characters of the two diseases are different. In 1917, Harter 

 ('17) described a pod blight of lima bean caused by Diaporthe 

 phaseolorum, whose pycnidial stage had previously been named 

 Phoma subcircinata but which rightfully belongs, as Harter 

 shows, in the form genus Phomopsis. Thus it is seen that the 

 lima bean organism in its pycnidial stage, the form commonly 

 found on diseased pods and leaves, falls into the same form genus 

 as the soybean organism. Likewise, the two diseases are similar 

 in general aspect and occur on related genera of host plants. In 

 view of these considerations, it might seem that the two diseases, 

 pod blight of lima bean and pod and stem blight of soybean, 

 are caused by the same pathogen. However, on the basis of the 

 differences noted below, the writer is led to consider the two 

 organisms as distinct species. 



1. The stroma associated with the pycnidia of the soybean 

 fungus is notably less well developed than that found associated 

 with the pycnidia of the lima bean organism. In the case of 

 Diaporthe phaseolorum the pycnidial stroma is rather extensively 

 broadened and often involves several pycnidia in a single stroma. 

 Likewise, the stroma is well developed beneath the pycnidium, 



causing its base to appear rather thick. In the case of the 

 pycnidia of the soybean fungus, on the contrary, this stroma is 

 little more than a thickening of the upper portion of the pycnidium 

 and is so sparsely developed beneath as to leave the base of the 

 pycnidium very thin. In fact, the stroma is often entirely 

 absent from the basal part of the pycnidium and the spore 

 cavity is separated from the host tissue by 2-4 rows of indis- 

 tinctly discernible fungous cells. 



