CRONARTIUM RIBICOL A 55 



The life-cycle may thus be represented as follows : 



i Basicliospore 



Mycelium 

 .Ecidium Spermogone 

 Female cells Spermatia 

 Fusion-cell 



Gametophyte J 

 (n generation) 



Sporophyte 

 (2/> generation) 



Spore-mother-cell 

 JScidio-teleuto- spore Intercalary cell 



o o 

 o o o o Basidiospores 



This life-history is especially worthy of consideration because 

 it probably represents that which obtained at the first evolution 

 of the higher Uredinales. The various types of development, 

 seen in the genera Puccinia, Uromyces, etc., and described 

 under the names Eupuccinia, Micropuccinia and so on, may all 

 be derived from this original form. See Grove, New Phytologist, 

 1913, p. 89. 



Cronartium ribicola. 



The Rust of Currants and Five-leaved Pines. 



This disease, called the Currant Rust in one stage, and the 

 Weymouth Pine Blister Rust in the alternate stage, can do 

 enormous damage in the second phase ; it threatens in places 

 to put a stop entirely to the cultivation of the Weymouth Pine. 

 It has been imported into England and the United States with 

 young trees of the latter from the continent of Europe. The 

 remedy is to inspect Weymouth Pines, in nurseries and plan- 

 tations, annually, cutting down and burning all those that 

 show infection, and to remove all currant bushes from their 

 neighbourhood. A currant-free belt, 300 — 500 ft. wide, is 

 considered sufficient for security. 



The teleutospores are produced on leaves of various kinds 



