228 
Journal of Agricultural Research 
Vol. VII, No. 5 
which are never attached to hyphae. Plate 12, fig. G, shows figures given 
by Home of spores of fungi associated with S. subterranea , and referred 
by him to species of Verticillium and Stysanus, and also drawings of the 
“bulbils" (PI. 12, fig. E) of Papulospora sp. found by the writers; the 
similarity between these is very striking. 
As early as 1883 Eidam (2, p. 411-414) called attention to the similarity 
between a species of Papulospora and one of the smuts. It is the “bul¬ 
bils" of Papulospora sp. that bear such a striking resemblance to the 
smuts and also to the spore balls of Spongospora subterranea . Hotson (4) 
published a paper that treats in part of the genus Papulospora and 
includes a good description of the “bulbil." In this paper he says (p. 
299): 
Lastly, among the structures which bear a striking resemblance to bulbils, the 
peculiar spore-balls of Spongospora subterranea (Vallr.) Johnson, should be mentioned; 
which although they might readily be taken for a species of Papulospora, have been 
shown to belong to the life-cycle of one of the Mycetozoa. 
In view of the recent isolation of Papulospora sp. by one of the writers 
from tubers affected with Spongospora subterranea this statement is very 
significant. A culture of this species of Papulospora submitted to 
Dr. J. W. Hotson was identified by him as Papulospora coprophila 
(Zukal) Hotson. All inoculations on the potato tuber with this fungus 
gave negative results. 
CONTROL MEASURES 
Although it has been known for more than 50 years that Spongospora 
subterranea occurs in most northern and central countries of Europe, very 
little effort has been concentrated on its control; and such studies as have 
been made apply only to local conditions in Ireland, where cultural, soil, 
and weather conditions are markedly different from those in the potato¬ 
growing sections of the United States. As soon, therefore, as it was 
found that the disease had become established in some of the leading 
potato-growing sections of this country, the study of its control became 
imperative and was undertaken by the writers along four lines: (1) Early 
harvesting, (2) seed treatment, (3) varietal response, and (4) soil 
treatment. 
Early harvesting 
That Spongospora subterranea develops on the tubers only after they 
are partially mature has already been shown. Although carefully sought 
for during the entire season of 1914 in the plots in which infected seed 
was planted, no infections were found on the crop until August 20; and 
not until about three weeks later did it become common or conspicuous. 
The first case of infection in the warehouse at Caribou was found on 
September 12 by the Maine Potato Inspection Service, which employed 
