208 



MYCOLOGY 



Belonging to the genus Gymnoconia (Fig. 92) is the orange rust 

 of raspberry and blackberry which is found throughout the United 

 States and Canada. It is also widely distributed in Europe and Asia. 



The genus Phragmidium, which is confined entirely to plants of the 

 rose family, is autoecious. Warts are formed on the teliospores by the 

 contraction of an outer gelatinous layer which with a rigid middle 

 lamina and the arrangement of the germ pores distinguishes Phrag- 



FiG. 78. — Teliospores of cedar apple showing germination with formation of 

 basidia (promycelia) and basidiospores (sporidia). {After Reed, H. S., and Crabill, 

 C. H., Techn. Bull. 9, Va. Agric. Exper. Stat., May, 1915.) 



midium from neighboring genera. The teliospores are two- to several- 

 celled by transverse septa. An important species is the Rust of Roses, 

 Phragmidium subcorticium, which has a spindle-shaped teliospore with 

 six to eight cells. 



Gymnosporangium is a genus of heteroecious rusts the secia of which 

 occur on Rosacea (except one on Hydrangeac^ and one on Myri- 



