348 UREDINEAE. 



present ; the palisade layer is doubled, and rupture of the 

 epidermis takes place ; chlorophyll-formation is suppressed, the 

 cell-sap becomes yellow, and starch tends to accumulate. 



P. dispersa may cause serious damage to wheat and rye ; P. 

 rvhigo-vera, also on barley and oats. The spore-patches are 

 found on stalks and leaf-sheaths more than on the lamina. The 

 myceliam may hibernate in grasses, so that the fungus is not 

 dependent on the aecidial stage ; for this reason the disease is 

 not easily combated. 



P. glumarum Eriks. et Henn. Golden-rust. This species, 

 hitherto generally included under P. ntbigo-vera (D. C.) has been 

 separated by Eriksson and Henning.^ Experimental infection 

 on Boragineae gave negative results. 



Eriksson distinguishes the following specialized varieties of 

 this species : 



A. Definite (and undoubtedly distinct). 



1. Var. tritici on Tritieum, vulgar e. 



2. Var. Jiordei on Hordeum mdgare (somewhat uncertain). 



3. Var. elymi on Elymus arenariv£. 



4. Var. agropyri on Triticum repens. 



B. Not sharply defined : 



5. Var. secalis on Secale cereale. 



The uredospore-sori are lemon-yellow in colour, and form 

 lines on the leaf-blade which may run together and reach a 

 length of 10 mm. The teleutospore-sori form long, fine, brown 

 or black lines : the sori are divided into numerous chambers, 

 each enclosed in a circle of curved brown paraphyses. The 

 spores germinate in the autumn of the same year. The pro- 

 mycelium is yellow till the spores are abjointed ; in this way 

 it is distinguished from P. dispersa. 



P. poarum Niels. (Britain). Uredo- and teleutospores on 

 Poa. According t.o Nielson, the aecidia occur on Tussilago, 

 Petasites, and Adenostyles. Fentzling (loc. cit.) has described 

 certain anatomical changes which accompany deformations due 

 to the aecidia. 



P. phlei-pratensis Eriks. et Henu. This has a hibernating mycelium 

 which produces uredospores continuously on Phleum and probably also 

 on Festuca. Aecidia have not as yet been observed. 



^Eriksson and Henniug {loc. cit.). 



