GRASS-RUST. 



417 



astrous effects on tliem us on wlieat. The red rnst or uredo 

 state appears from early spring until fall. It consists of micro- 

 scopic one-celled rough spores, borne on branches of a myceli- 



FiG. 161.— Grasa-rust. A, Kerminatlng teleutospore, (; B, promycelium, with spori 

 dia: C, 8 p, sporidium, germinating on the lower side of a leaf; u, a geriuinatint 

 uredospore.— (From DeBary,) 



ng 



itm that vegetates within the grass, and only appears on the sur- 

 face to fruit, which propagate the disease rapidly in damp warm 

 weather. Toward the end of the season the same mycelium 

 bears a second form of fruit — two-celled teleutospores or winter- 

 spores — that form dense elongated black cushions Avhere tliey 

 break through the epidermis, often covering the greater part of 



