PLATE 7 
Spongospora subterranea on Solatium tuberosum: 
Fig. A.—Stem of a potato showing formation of a gall caused by Spongospora sub¬ 
terranea . Note the discoloration and shrinkage near the point of formation. Although 
sometimes present, galls rarely occur on the stems. 
Fig. B.—Part of a stolon showing galls caused by Spongospora subterranea. 
Fig. C.—Discoloration so often found on the root near the point where the galls 
form. 
Fig. D.— Spongospora subterranea as found on the root system of the potato. The 
galls resemble nematode root galls or nitrogen nodules. Generally these galls appear 
on the roots before any sign of the disease is seen on the tuber. 
