284 



GENERAL MORPHOLOGY OF PLANTS 



449. The black rust of wheat (teleuto stage). On the 



mycelium which originates from the aecidiospores, in less abun- 

 dance on that which originates from the uredospores, another 

 kind of spore is formed, the teleutospore. These are either in 



B 



Fig. 259. 



A, section through sorus of black rust of wheat, showing teleutospores. B, mycelium 

 bearing both teleutospores and uredospores. (After cle Bary.) 



separate sori (a teleutosorus) or they are mixed in with the 

 uredospores. In the wheat rust the teleutospores are two-celled, 

 with thick brown walls, and the stalk usually remains attached 

 (ng. 259). 



450. Germination of the teleutospores and infection of 

 the barberry. The teleutospores of the wheat rust rest during 

 the winter on leaves and stems lying on the ground. In the spring 

 each cell germinates, putting forth a tube through a germ pore 

 near the apex of each cell. This tube is the promycelium, which 

 divides quite regularly by three cross walls into four cells, each of 

 which forms a small pointed outgrowth, the sterigma. Through 

 this the protoplasm in the cell moves out and forms a small spore, 

 the sporidium. This sporidium is carried by the wind to the 

 barberry, where it germinates, the tube enters between epidermal 



