CRONAETIUM. 



381 



host-plants, and several species produce blister-rust on the bark 

 of species of pine. 



Gronartium asclepiadeum (Willd) (U.S. America). Uredo- 

 and teleutospores occur on Cynanchum Vincetqxicum (perhaps 



Fig. 214. — Cronai'tium asclepiadeum oji Ct/nanch^m Vincetoxicum. The uredo- 

 sori sliow as spots, the teleutospore-sori as processes on the leaves, (v. Tubeuf 

 del) 



also on Gentiana asclepiadea). The aecidial stage, known as 

 Peridermium Oornui Eostr. et Kleb. produces a blister-rust on 

 the bark of Pinus sylvestris. 



Fig. 215. — Ci-onartium asclepiadeum. Section of a 

 Cynanchum leaf. The leaf -parenchyma is permeated with 

 mycelium, and sori are formed on the lower epidermis. 

 A, uredo-sorus ; B, teleutospore-sorus, many spores of 

 which have germinated and given off promyceHa with 

 sporldia. (v. Tubeuf del.) 



Brown spots may be found on the leaves of the Cynanchum''- 

 during July, August, and September (Fig. 214). On examina- 

 tion of the spots with a lens, the leaf-epidermis will be found 



^A very common plant in Europe though not indigenous to Britain. (Edit.) 



