1920] BISBY—UROMYCES 199 



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to find affiliations with other forms of rusts upon the same or similar 

 hosts through the various families, and such is the case. Under 

 the species U. heterodermus a considerable comparison with rusts 

 from related hosts is made, suggesting that certain groups of hosts 

 appear to harbor rusts characterized by various definite morpho- 

 logical characters. 



The geographical distribution of North American short cycle 

 species of Uromyces would indicate further that the mountainous 

 and more tropical regions furnish the most favorable location for 

 these forms. Only U. Rudbeckiae has a comparatively wide range, 

 a range including the plains area. 



Whether or not it is more than a coincidence that the absence 

 of pycnia and the occurrence of lepto-germination are found on 

 hosts higher in the evolutionary scale, the writer is not prepared 

 to say. 



Taxonomic 



With the progress of critical studies of North American rusts, 

 other short cycle forms will undoubtedly be separated out, and 

 further evidence secured as to the fixity and definiteness of the 

 life cycle in certain of these rusts. Uromyces heterodermus, for 

 example, was long placed with U. Erythronii, a correlated form. 

 It was found also that U. Bidentis was a short cycle form which 

 resembled U. bidenticola (P. Henn.) Arth. so far as characters of 

 teliospores are concerned. It is no doubt true that other short 

 cycle forms have been collected and placed with correlated long 

 cycle forms, although cultures are needed to determine the life cycle 

 in certain cases. 



The 11 species of Uromyces considered have several points of 

 similarity, one of which is the fact that all possess teliospores with 

 apices more or less thickened. In none of the species were para- 

 physes, stromata, isolated peridial cells, or other accompanying 

 structures found in the telia. 



Ke y 



Teliospores verrucose. 



Teliospores long, up to 43-47 fi 



Wall up to 1 . 5 /z thick 1. U. heterodermus 



Wall up to 2 . 5 /x thick 6. £\ nevadensis 



Telidspores short, up to 30 ju 5- V. Tranzschelii 



