LETTHR OF TRANSMITTAL. 



I 



U. S. Department of Agriculture, 



Division of Agrostology, 

 Washingto?}, D. C, April 9, 1900. 



Sir: I have the honor to transmit herewith the manuscript of a 

 paper entitl(>d A Revision of the North American Species of Bromus 

 Occurring- North of Mexico, prepared under my direction b}^ Mr. Cor- 

 nelius L. Shear, assistant agrostologist, and recommend the same for 

 publication as Bulletin No. 23 of this division, under the general title 

 of "Studies on American Grasses." 



The abundance of good material collected during the past few years 

 in the Rocky Mountains and the Northwest has shown the necessity of 

 a revision of the genus Broiu us. Until very recently good specimens 

 from these regions have been few, and their identification has rested in 

 many cases on tradition and misconceptions of the species. As an 

 illustration of this, the case of B. hreviari status may be cited. The 

 identiiication of this species was based by Thurber and Gray on speci- 

 mens distributed by Hooker under that name. These specimens when 

 compared with the original illustration of the species and the actual 

 type prove to be the old and well-known B. unioloides. The examina- 

 tion of portions of the types of Hooker, Link, and Nuttall has made it 

 possible to treat more satisfactorily the various forms from the same 

 region that have passed for B. ciliatus and its varieties. Thus B. 

 mdgaris^ which is one of the best-defined species of the Northwest, has 

 heretofore passed as B. ciliatus or B. purgans, or a variety of one or 

 the other. The group presenting the most difficulties in the way of 

 sati.sf actor}^ segregation is that to which B. carinatus and B. marginatus 

 belong. Here the forms and variations are so many and perplexing 

 that the present disposition of them is necessarily more or less tentative. 

 In the thorough study of the group Fournier's Mexican forms must be 

 considered, and these are so confused and poorly segregated that only 

 a comparison of his types can make a satisfactory disposition of them 

 possible. 



The present paper contains descriptions of 36 species and 28 varieties, 

 45 of which are natives and 19 introduced. The enumeration includes 

 a new subgenus, 3 new species, and 15 new varieties. 

 Respectfully, 



F. Lamson-Scribner, 



Agrostologist. 



Hon. James Wilson, 



Secretary of Agriculture. 



