ON GRAMINE.E 



259 



On leaves, culms and glumes of Agropyron caninum, A. 

 re pens, Brachypodium sylvaticum, Bromus mollis and other 

 species, Elymus arenarius, Hordeum vulgare, Secede Cereule, 



I). 



;.<•• 

 ..*' 



/ 



: a 



b 1 



Fig. 197. P. glumarum. a, uredo-sori and b, teleuto-sori, on leaves, nat. 

 size ; c, teleuto-sori, on glume ; d, uredospore ; e, teleutospore. 



Triticum vulgare. It is one of the few species that attack the 

 ears, to which it does serious damage. (Fig. 197.) 



This is one of two forms originally included under the collective name 

 P. Rubigo-vera DC. ; they can best be distinguished in the uredo-stage. 

 In the one, P. glumarum, the uredo-sori are abundant, clear lemon- or 

 sometimes orange-yellow, and stand in long lines, often occupying half the 

 leaf- blade ; in the other, P. dispersa and its subordinate forms, they tend 

 towards brownish-orange or even chocolate-brown, and are scattered, 

 rather thinly and without order, over the whole leaf-surface. Eriksson 

 and Henning first proved in 1896 what had been long surmised, that they 

 are quite distinct. P. glumarum has no known secidial form, and has 

 been divided into five biological races (see p. 67). It is common in certain 

 districts of England and is called the Spring Rust on account of its 

 early appearance, and Yellow Rust on account of its bright colour, which 

 varies from sulphur- to pale cadmium-yellow. The lines of the uredo-sori 

 may be as much as 7 cm. long, chiefly on the upper face of the leaf ; they 

 can be found all the year round on suitable leaves, and are frequently 

 abundant on Wheat as early as the beginning of May. The teleutospores 

 germinate as soon as they are mature ; the basidium is yellow until 

 the basidiospores are formed, not colourless as in P. dispersa. 



On Hordeum murinum there is recorded a form, P. Hordei Fckl., 

 which has smaller yellow sori, arranged less evidently in lines ; this may 

 belong to P. glumarum but has not yet been found in Britain. It is 

 probably not identical with P. simplex (q. v.). 



Distribution : Europe, Egypt, North America, Japan. 



17—2 



