DESCRIPTIONS OF AMERICAN UREDINE^, III. 



BY J. C. ARTHUR AND E. W. D. HO WAY 



The species of Uredinece to which this article is devoted 

 embrace those forms whose teleutospores occur on grasses 

 belonging to the tribes Maydeez, Aiidropogoiiccs, Paniccce, 

 Oryzcce, and Phalaridcce. In studying the plant rusts it 

 has been found very helpful to bring together all available 

 material on closely related hosts. In this way we have 

 been able to get a more comprehensive and accurate view 

 of the limitations and variations of species, and, moreover, 

 to detect a number of errors that have crept into the litera- 

 ture and led to misconceptions. To carry out this 

 plan we have taken the material for this article from the 

 hosts belonging to a circumscribed portion of the great 

 family of the Graminece ', rather than indiscriminately from 

 the hosts of any part of the family, as in the previous 

 article of the series. 



The present article like the two preceding ones, is based 

 upon the material in the authors' Uredinece Exsiccates ct 

 Iconcs, each article corresponding to a fascicle. The first 

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

 1895, and the second (4:377-402) December, 1898. The 

 first fascicle of the distribution was issued September, 1894, 

 and the second, December, 1898. 



The illustrations, which are the same for the Descriptions 

 and the Exsiccate?, 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 intimate association of host and parasite in case of 

 V— 2 7 



