PLATE SI 



A. — Yoiing sweet-potato roots affected with pox spots. 



B. — Sweet-potato sprouts, the lower rootlets of which have been totally destroyed 

 by pox. 

 C. — Typical pox spots on tubers of the Irish potato, 

 D. — Pox spots of the Irish potato (after Ramsey). 

 E. — Pox oa Irish potato showing lenticel infection. 



