PREFACE. 



The paper offered herewith, by Mr. David Griffiths, of the Bureau 

 of Plant Industry, United States Department of Agriculture, is a 

 systematic account of the grasses of the genus Bouteloua and closely 

 related genera, chiefly of the species found in North America. These are 

 native grasses, some of them among the most important constituents 

 of the natural pasturage of the West. Mr. Griffiths, in the 11 years 

 since the beginning of his study, has had extensive opportunity for 

 the observation of these grasses in the field, chiefly as engaged in the 

 investigation of the public stock ranges for the Department of Agri- 

 culture; has examined the specimens in the United States National 

 Herbarium and several other large herbaria; and, for the study of the 

 results obtained by others and the settlement of questions of nomen- 

 clature, has had at hand the resources of the Washington libraries. 



Frederick V. Coville, 

 Curator of the United States National Herbarium. 



