262 
Journal of Agricultural Research 
Vol. I, No. $ 
three different sets was sprayed with the spores suspended in water, but 
the disease was not produced thereby. Ten plants each of Ipomoea 
hederacea and Ipomoea purpurea , and 5 plants of Ipomoea coccinea were 
inoculated by inserting spores and hyphae into the lower part of the 
stem. Three plants of Ipomoea coccinea were infected, the other species 
not being injured by the fungus. 
Two sets of inoculations have been made with potatoes taken from 
storage. After inoculation one set was kept in the laboratory room in a 
cloth bag and gave negative results. In the other experiment the potatoes 
were placed in a damp chamber and kept moist with filter paper satu¬ 
rated with mercuric chlorid. Under these conditions the potatoes rotted 
readily. (PI. XXVIII, figs. A y B, C, and D.) The organism was 
recovered in pure culture from the pycnidia formed thereon and from the 
rotten tissue within. 
The results of these experiments show that the foot-rot organism is a 
vigorous wound parasite of Ipomoea batatas. In the greenhouse and 
in the field infection can be readily produced by wounding the plant, but 
this method is not imperative. It has been further shown that the tem¬ 
peratures and other environmental factors best suited for the growth of 
the plants are likewise most favorable for the development of the fungus. 
During warm, moist weather, when the plants grow most vigorously, the 
disease was more severe than when growth was retarded by low tempera¬ 
ture. Plants at all ages were about equally susceptible to the disease. 
It is also interesting to note in this connection that infection was 
readily produced by inoculating with hyphae only, the result showing 
that the progress of the disease was more rapid and the plants killed 
sooner than when inoculations were made with spores. 
HOW THE DISEASE IS PERPETUATED 
The exact life history of this fungus will be in doubt so long as a perfect 
stage is not known. It is evident, however, that an ascogenous stage is 
not necessary to carry it from one season to the next. Diseased speci¬ 
mens on which there were numerous pycnidia were wintered out in a 
wire cage covered over with leaves and some dirt with the hope that an 
ascospore stage might develop. On the 27th of the following April the 
specimens were examined, and normal pycnospores but no asci were 
found. 
A second lot of diseased specimens were wintered out in a wire cage 
set on the ledge of a north window, where they were subjected to alter¬ 
nately dry and w^et weather and other atmospheric changes. When these 
were examined on May 20, 1913, numerous normal conidia were present 
and the organism recovered in culture. 
There are at least two ways by means of which this disease may be 
carried from one year to another: (1) On the dead vines and (2) on the 
