Oct. a-Dec. 26,1916 
Illustrations 
IX 
Page 
PLATE 7. Spongospora subterranea on Solanum tuberosum: A.—Stem of a potato 
showing formation of a gall caused by Spongospora subterranea. B.—Part 
of a stolon showing galls caused by Spongospora subterranea. C.—Discol¬ 
oration so often found on the root near the point where the galls form. D.— 
Spongospora subterranea as found on the root system of the potato. 254 
Plate 8. Spongospora subterranea in the roots of various hosts: A.—Section 
through a potato root affected with Spongospora subterranea. B.—Several 
cells from Solanum warscewiczii y showing the formation of “giant cells” 
and their division into daughter cells. C.—Section through a tomato root, 
showing effects of infection by Spongospora subterranea . 254 
PLATE 9. Spongospora subterranea on the roots of various hosts: A.—Galls 
caused by Spongospora subterranea on the roots of Solanum warscewiczii. 
B, C.—Galls caused by Spongospora subterranea formed on the roots of the 
tomato.... 254 
PLATE IO. Injuries caused by Spongospora subterranea and other agencies: A.— 
Tuber showing the effect of flea-beetle injury. B.—Tuber showing a very 
early stage of infection by Spongospora subterranea. C, D.—Tubers grown 
in infected soil in the greenhouse under exceptionally moist conditions 
and allowed a long growing season. E.—A potato from Ireland showing 
the cankerous stage. P.—A tuber showing enlargement of the lenticels... 254 
Plate ii. Dryrot associated with Spongospora subterranea: A.—A potato tuber 
showing natural infection with Phoma sp. B, C.—Sections through tubers 
showing more advanced stages of a rot caused by a species of Phoma. D.— 
A potato tuber showing injury immediately around the sori, due partially 
to the work of the plasmodium. The lower side of the tuber also shows 
the beginning of the rot caused by Phoma sp. E.—Infection due to Phoma 
sp. on a potato tuber infected with Spongospora subterranea , followed by 
another, due probably to Fusarium coeruleum. F, H.—Potato tubers in¬ 
fected with Spongospora subterranea about three weeks after harvesting, 
showing the effects of desiccation injury. G.—Section through a tuber, 
showing the depth to which rot caused by Phoma sp. extends. 254 
Plate 12. Spongospora subterranea and Phoma tuberosa: A.—Section of potato 
tuber through a sorus around which no dryrot has as yet set in. B.—Sec¬ 
tion of a potato tuber made through a sorus of Spongospora subterranea after 
the tuber had been held in storage and some dryrot due to desiccation had 
developed. C, D.—Two views of the pycnidia of Phoma tuberosa as grown 
in pure culture. E.—Pycnospores. F. —Mature “bulbils” of Papulo- 
spora coprophila Hotson, which in the tissues of potato tubers may be 
mistaken for spore balls of Spongospora subterranea. G.—Spores of fungi 
associated with Spongospora subterranea and referred to Verticillium 
sp. and Stysanus sp. by Home, of whose drawing this figure is a repro¬ 
duction ... 254 
Plate 13. Phoma tuberosa on Solanum tuberosum: A, B.—Stages of the rot 
caused by Phoma tuberosa on the Irish potato. C, D, E-—Results of arti¬ 
ficial inoculation with pure cultures of Phoma tuberosa . 254 
Plate 14. Scab caused by Phoma tuberosa and Oospora scabies on Solanum 
tuberosum: A.—Section through a tuber affected with common scab. B.— 
Section through a tuber affected with the rot caused by Phoma tuberosa. .. 254 
