A REVISIO.^ OF THE NORTH AMERICAN SPECIES OF BROMUS 

 OCCURRING NORTH OF MEXICO. 



INTRODUCTION. 



It does not appear that any attempt has heretofore been made to revise 

 the species of Broimis of any very extensive region. In the present 

 paper the species of North America north of Mexico are treated. Those 

 of Mexico are so poorly known that no satisfactory disposition can be 

 made of them until more extensive collections have been examined and 

 the types of Fournier's species and varieties studied. A careful study 

 of the types of the species of Humboldt, Bonpland and Kunth and 

 Presl from the region of the Andes is also necessary in order to cor- 

 rectly understand our southwestern and Mexican species of the sub 

 genus Ceratochloa. 



The number of known species of Broimts, according to Bentham in his 

 "Notes on Graminese" in 1881, was about 40. This is the most recent 

 estimate, but according to Index Kewensis and the study of recent lit- 

 erature a total of 150 species would be a conservative estimate of the 

 number at present known. The number of species and varieties 

 described in this paper is 61. Of these 45 are indigenous, and the 

 remaining 19 adventive or introduced. Three are regarded as new 

 species, and fifteen as new varieties. A few species credited to North 

 America still remain doubtful or unknown to us. These have been 

 added at the end of the paper with their original descriptions. 



We desire here to acknowledge our great indebtedness and express 

 our thanks to the following botanists who have rendered valuable 

 assistance in the preparation of this paper, either by the loan or con- 

 tribution of material or by the copying of original descriptions or 

 plates: Drs. B. L. Robinson, Wm. Trelease, N. L. Britton, J. K. 

 Small, P. A. Rydberg, and I. Urban, also Sir W. T. Thiselton-Dyer, 

 Miss Alice Eastwood, and Prof. C. V. Piper. 



CLASSIFICATION. 



i The first step necessary in revising a genus is to decide what shall 

 I be considered its type. Then follows the question of its limitations, 

 i In this case, as in so many others, Linnaeus, who is cited as the author 



