194 BOTANICAL GAZETTE [march 



Characters and relationships 



The rusts considered in this paper are those which fulfil the 

 following requirements : 



Cycle of development includes only pycnia (sometimes) and telia, both 

 subepidermal. 



Pycnia deep-seated, globose or flask-shaped, with ostiolar filamepts. 



Telia erumpent, usually grouped; teliospores free, pediceled, i -celled; 

 wall firm, colored, smooth or variously sculptured; germination by a single 

 promycelium from an apical pore. 



Urediniospores normally absent but occasionally found in the telia. 



The association of pycnia with telia has for some time been con- 

 sidered the criterion of short cycle rust (i, 4). The occurrence of 

 definite aecia or uredinia (providing the evidence indicates that the 

 aecia or uredinia belong with the telial stage present) suffices to 



specimen from 



While 



some suspicion may be aroused by the presence of urediniospores, 

 such spores occasionally occur in the telia. In the cases in which 

 pycnia are only rarely or not at all produced, telia only being 

 present, the arrangement and character of the telia usually may be 

 utilized to indicate whether or not the specimen is short cycled; 

 a grouping of the telia in definite circinating or crowded groups, 

 or the occurrence of germination of the teliospores at or soon after 

 maturity, usually means that such a specimen belongs with the 

 group of rusts here treated. In certain cases, however, the telia 

 are diffused, and other considerations must be brought to bear. 

 A study of the Uromyces forms of the rusts as represented in 



herbarium and of the literature indicates that 



America 



forms 



Dietel (10) pointed 



of rusts is higher in proportion to the isolation of the geographical 

 region; that Uromyces shows a higher percentage of species in 



warmer 



New 



the 



I the number of species of Uromyces is about one-third 

 number of species of Puccinia. It is to be noted that, so 

 far as known, 8 of the 1 1 short cycle species of Uromyces are endemic 

 to North America, and only 1 of the 1 1 species occurs also in Europe. 



