192 



MORPHOLOGY. 



407a. Teleutospores the last stage of the fungus in the season. The teleu- 

 tospores are developed late in the season, or late in the development of the 



host plant (in this case the 

 wheat is the host). They 

 then rest during the winter. 

 In the spring under favor- 

 able conditions each cell of 

 the teleutospore germi- 

 nates, producing a short 

 mycelium called a promy- 

 celium, as shown in figs. 

 222, 223. This promy- 

 celium is usually divided 

 into four cells. From each 

 cell a short, pointed pro- 

 cess is formed called a 

 '* sterigma." Through this 

 the protoplasm moves and 

 Fig. 221. forms a small gonidiumon 



Germ tube entering the ,, , ,. , 



af through a stoma. the end, sometimes called 



a sporidium. 



408. How the fungus gets from the wheat back to the barberry. If these 

 sporidia from the teleutospores are carried by the wind so that they lodge on 



Germinating uredospore of 

 wheat rust. (After Marshall- leaf through a stoma 

 Ward.) 



Fig. 222. Fig. 223. Fig. 224. 



, Teleutospore g e r m i - Promycelium of ger- Germinating sporidia entering leal 

 nating, forming promy- initiating teleutospore, of barberry by mycelium, 

 celium. forming sporidia. 



Figs. 222-224. Puccinia graminis (wheat rust). (After R4arshall-Ward.) 



