CHAPTER XXI. 



FUNGI CONTINUED (RUSTS AND SAC FUNGI). 



' Rusts" (Uredineae). 



288. The fungi known as "rusts" are very important ones 

 to study, since all the species are parasitic, and many produce 

 serious injuries to crops. 



289. Wheat rust (Puccinia graminis). The wheat rust is 

 one of the best known of these fungi, since a great deal of study 

 has been given to it. One form of the plant occurs in long 



Fig- 145- 



Wheat leaf with red 

 rust, natural size. 



Fig. 146. 

 Portion of leaf 

 enlarged to show 

 sori. 



Fig. 147. 

 Natural size. 



Fig. 148. 

 Enlarged. 



Fig. 149. 

 Single 



Figs. 145, 146. Puccinia graminis, red-rust stage (uredo stage). 

 Figs. 147-149. Black rust of wheat, showing sori of teleutospores. 



reddish-brown or reddish pustules, and is known as the " red 

 rust" (figs. 145, 146). Another form occurs in elongated black 

 pustules, and this form is the one known as, the ' ' black rust ' ' 



129 



