400 



Diseases of Economic Plants 



Rust {Cronartium cerebrum. (Pk.) H. & L., Peridermium) . — 

 Swollen areas occur upon the branches and young stems 

 which are gradually killed. The gall-like growth sheds a 



Fig. 212. — Gall j)rt)(lucc(l by Cronartium (Perider- 

 mium) cerebrum on pine. After Hedgcock. 



profusion of orange-colored spores each spring. Chiefly by 

 its interference with the sap current the swellings bring about 

 the death of many trees. The galls are perennial and 



may 



