DESCRIPTIONS OF AMERICAN UREDINE^, IV. 



BY J. C. ARTHUR AND E. W. D. HOWAY. 



The following descriptions apply to American plant-rusts 

 inhabiting species of Graminece. belonging to the sections 

 AgrostidecR and Chloridecc, with their accompanying aecidia 

 so far as known. Of the sixteen species included in this 

 paper, only one, however, has had its full cycle of develop- 

 ment traced. That one is the very conspicuous rust on the 

 leaves of cord grass, which produces aecidia on ash trees, 

 and in the latter stage also occasionally attracts much atten- 

 tion. 



The present article, like the three preceding ones, is based 

 upon the material in the authors' Ufedinem Exsiccatce et 

 /cones, each article corresponding to a fascicle. The first 

 article was published in this journal (3:44-57) March, 1895, 

 the second (4:377-402) December, 1898, and the third 

 (5:171-193) May, 1901. 



The illustrations, which are the same for the Descriptions 

 and the Exsiccatce, are from camera-lucida drawings made 

 directly from the material of the distribution. The figures 

 and the packets have the same numbering, Arabic numbers 

 being used to designate species, and letters to indicate the 

 collections under each species. 



The numerals O, I, II, III, X, are used to designate the 

 spermogonial, aecidial, uredo, teleutosporic, and amphisporic 

 stages of the rust. When placed in capital type the material 

 employed for study and distribution showed well developed 

 sori, when in lower case type, thus, o, i, ii, iii, x, the particular 

 stage so indicated was in comparatively small amount or 

 inferior development. 



