PUCCINIA 231 



II. ^ECIDIOMYCETES 



PUCCINIA GRAMINIS (JEcidium Berberidis), Rust 

 of Wheat 



A. Pucdnia Stage. 



I. On the stems and leaves of wheat and others of the 

 Gramineae in winter, dark oblong patches may often be found, 

 which owe their origin to a Fungus (Pucdnia graminis) that 

 infests the tissues, and produces 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 : each 

 dark patch will be seen to be opposite one of the spaces be- 

 tween the vascular bundles, while the epidermis, which normally 

 covers over the tissues, is ruptured. In case it is the leaf 

 which has been cut, dark patches may be observed as rupturing 

 and projecting through the epidermis of both the upper and 

 lower surfaces. . 



Put on a high power, and in a thin section observe 

 i. The thin hyphae of the branched mycelium of the parasite 

 (Pucdnia), which ramify in the softer, succulent tissues, but do 

 not as a rule attack the sclerenchyma, or vascular bundles : 

 they may be traced up to the dark patches above noted. 



