UKEDINE.E 



637 



known as 'mildew,' produced by the attacks of the parasitic fungu.s 

 Pucdnia graminis. It was long ago observed that wheat WMS 

 especially liable to this disease in the vicinity of barberry bushes ; 

 and it is now known that a fungus parasitic on barberry leaves, for- 

 merly known as JEcidium berberidis, is the ' secidiospore ' generation 

 of the same species of which Puctinia graminis is the ' teleutospoiv ' 



X 



FIG. 475. Pucdnia gra/ninis. From De Bary's ' Comparative Morphology and 

 Biology of the Fungi.' (The Clarendon Press.) A, portion of leaf of Berber/* 

 with young ajcidium; I., section through leaf containing a?cidia : /, spermo- 

 gones; a, aacidia opened ; p, peridium ; II., group of ripe teleutospores 

 bursting through the epiderm e in leaf of Tritic.um i-t'j>en ; /, teleutospores; 

 III., teleutospores t, and uredospores nr; I. slightly magnified ; II. x 190; 

 III. x 390. 



generation. The complete cycle of development of the best known 

 UredinecB, such as the mildew (fig. 475), is this. The form known as 

 Pucdnia graminis produces teleutospores, thick-walled spores, borne 

 usually in pairs, at the extremity of elongated cells known as basids 

 or stemgmata. Each of these teleutospores gives rise, on germinating 

 within the tissue of the grass, to a hypha or ppomycele, the terminal 

 cells of which develop, on slender basids. each a -single spore or 



