INJURIOUSNESS OF WEEDS 



679 



Fig. 526. Rusts of cereals also occur on weedy grasses, like Squirreltail Grass, 

 Wild Oats, etc. Puccinia graminls : A, "winter" or teleutospore ; t, ger- 

 minating, B, germ-tube (promycelium) with lateral sporidfia sp. C, 

 epidermis of under surface of leaf of barberry showing crescent shaped 

 cells of stoma and the germinating sporidium sp at i penetrating the 

 epidermis. D, uredo spore germinating after being in water fourteen hours. 

 E, Puccinia rubigo-vera, the upper cell has germinated. C. D. E, magnified 

 390 times, the other somewhat more. (After DeBary. ) P, Puccinia gram- 

 inis, Pers. ; both cells have germinated ; a, a sporidium germinating, magni- 

 fied 600 times. (After Bolley.) G, Puccinia coronata Cda. ; teleutospores 

 of rust on leaves of oats, magnified about 600 times. (After Bolley.) 



