434 



FUNGOUS DISEASES OF PLANTS 



fungus should not long ago have appeared in America. 1 The 

 gecidial stage is also found upon another species of pine, Pi mis 

 cnnbra, and it is believed by some that the fungus is indigenous 

 upon this species in Russia and in Switzerland. 



Host plants. The uredo and teleuto stages (Fig. 211) occur 

 upon many varieties of the genus Ribes, representing several 



FIG. 211. CRONARTIUM RIBICOLA 



a, sori on currant leaf ; , sorus and teleutosporic column ; c and d, 

 uredospores and teleutospores 



1 During June, 1909, the secidial stage of this fungus was found in a nursery 

 of three-year-old white pine seedlings imported from Germany. Many seedlings 

 of this importation have been distributed to several northeastern states and to 

 Canada. A determined effort is being made to inspect all plantings, to destroy 

 the diseased stock, and also to prevent further importation of the infected white 

 pine seedlings. Inspection of such seedlings at the time of importation is prac- 

 tically valueless, since the fungus has an incubation period in the bark of nearly 

 one year before the characteristic swellings appear. Details of the outbreak in 

 New York are discussed in the following articles : 

 Atwood, G. G. Blister Rust of Pines and the European Currant Rust. Dept. 



Agl., State of N. Y. Ilort. Built. 2 : 1-15. 1909. 

 Spaulding, Perley. European Currant Rust on the White Pine in America. 



Bur. Plant Ind., U. S. Dept. Agl. Circular 38 : 1-4. 1909. 



