FIG. 198. Wheat rust (Purcinia graminis) 



A, part of a wheat plant showing rust spots on the stalk. B, a small section of a 

 wheat leaf uj>on which the parasitic rust is growing: m, mycelial hypha of the 

 rust; y.u, young summer spore, or uredospore; n, fully formed uredospore; st, 

 upright hypha upon which uredospore is formed. C, germination of uredospore: 

 st, old hypha; , old uredospore wall ; m, new mycelial hyphre. D, winter spore, 

 or teleutospore : st, hypha ; t, two-celled spore. E, germination of teleutospore (0 : 

 at, old hypha ; p, new hypha, or the promycelium ; s, spores, or sporidia. F, sec- 

 tion of the barberry leaf, showing ascidiospore stage of rust: e l upper epidermis, 

 and e 2 lower epidermis ; p, wall of cup, or tecidinm ; , aecidiospores. All much 

 enlarged. Rearranged from Duggar's " Fungous Diseases of Plants " 

 266 



