Oct. 30, 1916 
Spongospora subterranea and Phoma tuberosa 
227 
which they isolated from the sori of S. subterranea were largely respon¬ 
sible for this confusion and error. 
Wallroth saw in the spore balls of Spongospora subterranea a striking, 
resemblance to the smuts and accordingly described the organism as 
Erysibe subterranea. Berkeley (1) more than 20 years after Wallroth’s 
observations published a drawing of two spore forms in connection with 
an article on the potato murrain and refers these two forms to the spores 
of Tubercinia sp. Fr., which cause a scab. The spore forms shown in 
Berkeley's drawings are certainly not the spore balls of 5 . subterranea , as 
the former show a distinct pedicel, but Berkeley’s description of their 
effect on the tuber is highly suggestive of the latter fungus. The surface 
of the potato, he says, is “covered with pustules, which at length become 
cup-shaped and are powdered within with an olive-yellow meal consisting 
of the spores of a fungus.” The drawings and description of the fungus 
create some doubt as to whether he referred to 5 . subterranea. In view 
of his illustration and statement that he saw the various stages of growth 
attached to flocci, it is possible he was working with material which in 
addition to being infected with 5 . subterranea was contaminated with the 
“bulbils” of Papulospora sp. or with the forms referred to by Home (3) 
The presence of fungus hyphae in the sorus and the consequent hypoth¬ 
esis that there are two kinds of powdery-scab is shown by the following 
statement by Johnson (5, p. 172): 
In some Scotch material I examined, hyphae were clearly present in the scab areas 
outside of the cellular tissue of the tuber, and though some could be accounted for as 
the mycelial hyphae of Rhizoctonia scab there were others not so explicable. The 
hyphae are swollen, septate, and branching; their contents abundant and granular. 
In some case chains or masses of spores may be seen arising from the protoplasmic 
contents of the hyphae. Spongy spore-balls, very like those of Spongospora, arise, 
and ultimately the inclosing walls of the hyphae disappear and leave the balls lying 
free. The more external balls lose their compactness and break up into single spores 
or small groups of spores, so that they form a finer powder than Spongospora, whose 
spore-balls remain intact to the end. The mode of origin of the spores is not unlike 
that met with in the Ustilaginea , so far as they have been studied; and it thus appears 
as if . . . there are two kinds of potato scab characterized by powdery spore-balls, the 
one with a plasmodium— Spongospora subterranea Wallr.—the other a Hyphomycete, 
possibly one of the Ustilaginaceae. 
Horne (3, p. 377, 380) says: 
If spore-balls are present, they are frequently associated with the hyphae of various 
fungi—the association is so close in some instances that it is difficult to convince one¬ 
self that the spore-balls are not the reproductive bodies of the fungus. ... In late 
stages of the disease, and even in the powdery-scab stage, the spore-balls . . . are 
frequently intimately associated with the hyphae of various fungi. The spore-balls 
appear sometimes to be attached to hyphae, or hyphae twine around them and link 
them together. 
These statements are indeed significant and show that extreme care 
must be taken in identifying the spore balls of Spongospora subterranea , 
55859 °— 16 - 2 . 
