PLATE XVIII 

 Tuber-rot from Pennsylvania caused by Fusarium eumartii, n. sp.: 



Fig. I, 2. — External and sectional view of the same potato tuber. The spots in the 

 center of figtire 2 are not pertinent. 



Fig. 3, 4. — Sectional views of other potato tubers. 



Fig. 5. — A cross section of a potato tuber showing how the fungus frequently follows 

 the tissue adjacent to the btmdle ring. 



