246 



RUSTS (UREDINE./E) 



appropriate Grass, whereupon hyphse grow out through special 

 thin areas of the wall (Fig. 131, /), to start a fresh generation 

 of the Rust. In this way the disease rapidly spreads during 

 the summer months. 



In rare cases the Fungus may persist through the winter by 



Fig. 131. — Rust of Wheat (Puccinia graminis). a, small part of leaf of 

 Barberry, showing a group of iccidia ; b, group of uredospores (».) 

 and one teleutospore [t.) ; c, germinating teleutospore (only the hypha 

 growing from one of the two cells is shown at its full length), with 

 developing basidiospores {ba.) ; d, group of teleutospores, seen in 

 section of loaf of Wheat ; e, section of Barberry-leaf, showing cluster- 

 cups or Eccidia {ae.) in two stages of development, and spermogonia 

 (s.) ; /, germinating uredosporc. (b, d, and/ after De Bary ; c after 

 Tulasne ; e after Sachs.) 



means of these spores, and possibly also as a parasite on wild 

 Grasses. As a general rule, however, special winter- or idcido- 

 spores arc produced towards autumn, and these remain dormant 

 in the soil until the following spring. The formation of teleuto- 

 spores is evidenced by a darkening of the spots on the Grass- 

 leaves. Microscopic examination shows that they are now caused 



