234 



PLANT DISEASES 



continuance, the only course is to remove the one con- 

 sidered as of least value. 



Fig. 59. Cronartium ribicolum. i, uredo and teleuto- 

 spore stages on leaf of black currant ; 2, uredospores, 

 a, and teleutospores, b, cemented together to form an 

 erect, hairlike structure, x 50 ; 3, uredospore, x 300 ; 

 4, four teleutospores, two of which are germinating, and 

 one of the germ-tubes has produced four promycelium 

 or secondary spores, x 300 ; 5, aecidia on bark of Wey- 

 mouth pine ; 6, aecidiospores, x 300. 



Rostrup, Bot. Centralb, xliii. p. 353. 



Prillieux, Malad. des Plantes Agric., vol. i. p. 275. 



