PR EFACE. 



The present volume of the Contributions from the United States 

 National Herbarium consists of seven papers. 



The first paper, by Charles V. Piper. :L North American Specie- of 

 Festuca," was prepared in the Office of the Agrostologist, Department 

 of Agriculture, but in view of the fact that it was of a strictly sys- 

 tematic — not agricultural — character, it was offered to the National 

 Museum for publication and was accepted. The author of the manu- 

 script regrets that it was not possible to consult all the type specimens 

 of the American species, several of which are in European herbaria, 

 but he considers it preferable to offer his work for publication now 

 rather than to delay it indefinitely. 



The second paper, entitled "The Genus Ptelea in the Western and 

 Southwestern United States and Mexico," by Dr. Edward L. Greene, 

 Associate in Botany. United States National Museum, is the result of 

 an exhaustive study of the western species of Ptelea. Doctor Greene 

 finds that this genus, instead of being composed of only a few species, 

 is a very large one, and describes 59 species, of which 55 are new. 

 His work is based chiefly on the large series of specimens in the 

 National Herbarium, in his own collection now deposited here, and in 

 (apt. John Donnell Smith's, eventually to come here, together with 

 the collections of the late C. C. Parry and that of the California 

 Academy of Sciences. The types are chiefly in the National 

 Herbarium, and unless otherwise indicated are to be understood as 

 belonging here. 



The third paper consists of the fifth number of "Studies of Mexi- 

 can and Central American Plants." by Dr. J. N. Rose, Associate 

 Curator, Division of Plants, United States National Museum. Doctor 

 Pose has made five journeys to Mexico, each of which has resulted in 

 the acquisition of a valuable collection for the National Herbarium 

 and in a published report. Each of these reports, like the accom- 

 panying one 1 , covers only fragmentary portions of his whole work. 

 All, however, are devoted to the elucidation of tin 4 . ame general 

 subject, the flora of central Mexico, and together they form a highly 

 valuable series of contributions to our botanical knowledge of that 

 region. 



The fourth paper is "The Leguminosae of Porto Rico." by Miss 

 Janet Russell Perkins, PI). D. In L90] and L902 Miss Perkins, under 



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