18 



STRUCTURE AND CLASSIFICATION OF FUNGI 



The aeciospores can infect only wheat, barley, oats, rye, and cer- 

 tain wild grasses. They do not infect barberry. They give rise to 

 a mycelium with paired nuclei, the dikaryon, which eventually forms 



Fig. 9. Section through a red pusl^le on wheat affected with Puccinia graminis 

 showing the formation of urediospores. 



Fig. 10. Section through a black pustule on wheat affected with Puccinia 

 graminis showing the formation of teliospores. 



another kind of spore, the urediospore (uredospore, urediniospore) . 

 These are produced singly on the sporophore, and are binucleate. 

 They are reddish in color and form the red pustules on wheat leaves 



