MANUAL OF THE GRASSES OF THE UNITED STATES 



13 



SCOPE OF THE MANUAL 



(The manual includes descriptions 

 of all grasses known to grow in the 

 continental United States, excluding 

 Alaska. There are 169 numbered gen- 

 era and 1,398 numbered species. Of 

 these, 46 genera and 156 species are 

 introduced, mostly from the Eastern 

 Hemisphere. 



In addition to the numbered spe- 

 cies, which may be considered per- 

 manent constituents of the flora of 

 the United States, there are 16 genera 

 and 120 species that are known only 

 as ballast plants, or as waifs, or are 

 only rarely cultivated. These appear 

 not to be established and are men- 

 tioned, without numbers, in para- 

 graphs appended to their nearest al- 

 lies. They are not included in the keys. 



The manual is based mainly on the 

 material in the United States Na- 

 tional Herbarium, the grass collection 

 of which is the largest in the world, 

 numbering more than 320,000 sheets. 

 In addition, all the larger collections 

 of grasses in the United States have 

 been consulted and the curators have 

 lent specimens for study and have 

 aided in other ways. Many smaller 

 collections have contributed informa- 

 tion, especially on the ranges of spe- 

 cies. The cooperation of the Forest 

 Service, United States Department of 

 Agriculture, has been invaluable. The 

 Forest Service maintains in its Wash- 

 ington office a range-plant her- 

 barium consisting of the collections 

 made by forest officers, especially 

 those located in western national 

 forests and forest experiment stations. 

 The grasses of this range-plant her- 

 barium have been examined and have 

 furnished important data on distribu- 

 tion. 



Many botanists throughout the 

 country have rendered valuable as- 

 sistance in recent years by contribut- 

 ing specimens that have added spe- 

 cies previously unknown from the 

 United States, have extended ranges, 

 and have helped to solve the position 

 of puzzling species and varieties. 4 



Nearly all the numbered species are 

 illustrated. 5 About half are accom- 

 panied by a map, giving the distribu- 

 tion of that species in the United 

 States. 



To aid the users of this work in pro- 

 nouncing the Latin names the ac- 

 cented syllable is indicated. The ac- 

 cent mark is used to show the ac- 

 cented syllable without reference to 

 the length of the vowel. 



GRAMINEAE (POACEAE), THE 

 GRASS FAMILY 



Flowers perfect (rarely unisexual), 

 small, with no distinct perianth, ar- 

 ranged in spikelets consisting of a 

 shortened axis (rachilla) and 2 to 

 many 2-ranked bracts, the lowest 2 

 being empty (the glumes, rarely one 

 or both obsolete), the 1 or more suc- 

 ceeding ones (lemmas) bearing in 

 their axils a single flower, and, be- 

 tween the flower and the rachilla, a 

 second 2-nerved bract (the palea), the 

 lemma, palea, and flower together 

 constituting the floret ; stamens 1 to 6, 

 usually 3, with very delicate fila- 

 ments and 2-celled anthers; pistil 1, 

 with a 1-celled 1-ovuled ovary, 2 



4 The more important are: A. A. Beetle, from Cali- 

 fornia; E. E. Berkeley, from West Virginia; H. L. 

 Blomquist, from North Carolina; W. E. Booth, from 

 Montana; Clair Brown, from Louisiana; V. H. Chase, 

 from Illinois, Arkansas, and Idaho; Earl Core, from 

 West Virginia; R. A. Darrow, from Arizona; R- jJ« 

 Davis, from Idaho; Charles C. Deam and J- E. 

 Potzger, from Indiana; H. I. Featherly, from Okla- 

 homa; M. L. Fernald, from Northeastern States and 

 Virginia; A. O. Garrett, from Utah; L. N. Goodding. 

 from the Southwest; F. W. Gould, from Arizona and 

 California; C. R. Hanes, from Michigan; H. D. 

 Harrington, from Colorado; Bertrand Harrison, from 

 Utah; R. F. Hoover and John Thomas Howell, from 

 California; T. H. Kearney, from Arizona; John and 

 Charlotte Reeder, California to Michigan; and W. A. 

 Silveus, from Texas and other Southern States. 



Jason R. Swallen, Curator, Division of Grasses, 

 U.S. National Museum, has given valuable assistance. 

 The bibliography is based on the catalog of grass 

 names maintained in the Division of Grasses, this 

 catalog being the work, over some 35 years, of Cornelia 

 D. Niles, bibliographer. F. A. McClure, bamboo spe- 

 cialist, U.S. Department of Agriculture, contributed 

 the economic notes on bamboos and has aided in the 

 elucidation of the native species of bamboos. 



6 The drawings illustrating the genera (previously 

 published in the U. S. Department of Agriculture 

 Bulletin 772, the Genera of Grasses of the United 

 States . . . ) and nearly half of the others were made by 

 Mary Wright Gill; the rest were drawn by Edna May 

 Whitehorn, Frances C. Weintraub, Leta Hughey, and 

 Agnes Chase. The last-named made most of the 

 spikelet drawings. In each case the specimen from 

 which the drawing was made is cited, for example 

 (Nash 2198, Fla.). 



