462 PRACTICAL BOTANY 



II. ^CIDIOMYCETES 



PUCCINIA GRAMINIS (-fficidium Berberidis), 

 Rust of Wheat 



A. Pnccinia Stage 



I. There may often be found on the stems and leaves 

 of wheat and others of the Graminese in winter, dark 

 oblong patches, which owe their origin to a Fungus 

 (Puccinia graminis) that infests the tissues, and pro- 

 duces the disease called Rust. 



Examine one of these patches with a lens, and note 

 that the superficial tissues of the wheat are ruptured 

 by a longitudinal slit, and the torn edges are turned 

 back, so as to expose a dense, dark -coloured mass, 

 which protrudes from within : the nature of this mass 

 must be studied by means of sections. 



II. Cut transverse sections of the leaf-sheath, or other 

 diseased part of the Grass plant, taking care that the 

 section shall traverse one or more of the dark patches 

 of Rust : mount in glycerine, and examine under a low 

 power. Observe that the structure of the greater part 

 of the section is normal (see page 175, &c.) : the dark 

 patches will be seen to be opposite one of the spaces 



