A D F 
Fic. 198. Wheat rust (Puccinia graminis) 
cf, part of a wheat plant showing rust spots on the stalk. B, a small section of a 
wheat leaf upon which the parasitic rust is growing: m, mycelial hyphe of the 
rust; y.u, young summer spore, or uredospore; wv, fully formed uredospore; st, 
upright hypha upon which uredospore is formed. C, germination of uredospore: 
st, old hypha; u, old uredospore wall; m, new mycelial hyphe. D, winter spore, 
or teleutospore: st, hypha; t, two-celled spore. EZ, germination of teleutospore (t) : 
st, old hypha; p, new hypha, or the promycelium ; s, spores, or sporidia. F’, sec- 
tion of the barberry leaf, showing ecidiospore stage of rust: e; upper epidermis, 
and eg lower epidermis; p, wall of cup, or ecidium; s, zecidiospores. All much 
enlarged. Rearranged from Duggar’s “ Fungous Diseases of Plants” 
255 
