PREFACE. 



The accompanying paper, entitled The North American species of 

 Panicum, by A. S. Hitchcock, Systematic Agrostologist of the United 

 States Department of Agriculture, and Agnes Chase, Assistant in 

 Systematic Agrostology, is the result of an exhaustive study of the 

 material of this genus in the United States National Herbarium and 

 in the other large herbaria of the United States. All the more impor- 

 tant herbaria of Europe were visited by Mr. Hitchcock for the purpose 

 of examining the type specimens of American species described by 

 European authors. This opportunity is taken to acknowledge the 

 many courtesies extended by the curators of the herbaria visited. 

 In addition to the knowledge of the genus gained through an exami- 

 nation of many thousand herbarium specimens, the authors have 

 had opportunity to collect material throughout the United States 

 and have observed nearly all the species of that region in their native 

 habitats. Because of the lack of material and of the necessary field 

 studies, it has been impossible to present the species of tropical 

 America with the same degree of detail as the species of the United 

 States, but it has seemed advisable to include these tropical species 

 in order to bring together in one paper our present knowledge of the 

 genus in North America. 



The authors describe 197 species and 8 subspecies, each of which 

 is accompanied by a text figure illustrating the spikelet and fruit. 

 The descriptions of species occurring within the limits of the United 

 States are also accompanied by an outline map graphically represent- 

 ing the geographical distribution. 



Frederick V. Coville, 

 Curator of the United States National Herbarium. 



in 



