MANUAL OF THE GRASSES OF THE UNITED STATES 15 



able. The Forest Service maintains in its Washington office, a range- 

 plant herbarium, consisting of the collections made by forest officers, 

 especially those located in western national forests and forest experi- 

 ment stations. The grasses of this range-plant herbarium have been 

 placed at the disposal of the writer and have furnished important 

 data on distribution. 



Many botanists throughout the country have rendered valuable 

 assistance in recent years by contributing specimens which have 

 added species 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 species have been illustrated. 5 



To aid the users of this work in pronouncing the Latin names the 

 accented syllable is indicated. The accent mark is used to show the 

 accented syllable without reference to the length of the vowel. 



GRAMINEAE (POACEAE), THE GRASS FAMILY 



Flowers perfect (rarely unisexual), small, with no distinct perianth, 

 arranged in spikelets consisting of a shortened axis (rachilla) and 2 to 

 many 2-ranked bracts, the lowest two being empty (the glumes, rarely 

 one or both obsolete), the one or more succeeding ones (lemmas) 

 bearing in their axils a single flower, and, between 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 filaments and 2-celled anthers; pistil 1, with a 1-celled 

 1-ovuled ovary, 2 (rarely 1 or 3) styles, and usually plumose stigmas; 

 fruit a caryopsis with starchy endosperm and a small embryo at the 

 base on the side opposite the hilum. 



Herbs, or rarely woody plants, with hollow or solid stems (culms) 

 closed at the nodes, and 2-ranked usually parallel-veined leaves, these 

 consisting of two parts, the sheath, enveloping the culm, its margins 

 overlapping or sometimes grown together, and the blade, usually 

 flat; between the two on the inside, a membranaceous hyaline or 

 hairy appendage (the ligule). 



The spikelets are almost always aggregated in spikes or panicles at 

 the ends of the main culms or branches. The perianth is usually repre- 

 sented by 2 (rarely 3) small hyaline scales (the lodicules) at the base 

 of the flower inside the lemma and palea. The grain or caryopsis (the 

 single seed and the adherent pericarp) may be free, as in wheat, or 

 permanently enclosed in the lemma and palea, as in the oat. Rarely 

 the seed is free from the pericarp, as in species of Sporobolus and 

 Eleusine. The culms of bamboos are woody, as are also those of a 



< The more important are: Brother G. Arsene, Sacred Heart Training College, Las Vegas, N.Mex., 

 collections from Louisiana and New Mexico; H. L. Blomquist, Duke University, Durham, N.C., collec- 

 tions from North Carolina; B. F. Bush, Courtney, Mo., collections from Missouri and Texas; V. H. Chase, 

 Peoria, 111., collections from Illinois; Charles C Deam, research forester, Indiana, collections from Indiana; 

 H I Featherly, Agricultural and Mechanical College, Stillwater, Okla., collections from Oklahoma; the 

 late William C Ferguson, Hempstead, N.Y., collections from Long Island; A. O. Garrett, East High School, 

 Salt Lake City, collections from Utah; James E. Nelson, Salem, Oreg., collections from Oregon including 

 ballast plants near Portland; J. B. S. Norton, University of Maryland, collections from Maryland; W. A. 

 Silveus, San Antonio, Tex., collections from Texas, especially in the vicinity of San Antonio, including 

 several novelties; B. C. Tharp, University of Texas, collections from Texas. 



s The drawings illustrating the genera (previously published in 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 remainder were drawn by Edna May Whitehorn; the spikelet drawings are by Agnes 

 Chase. In each case the specimen from which the drawing was made is cited, for example (Nash 2198, 

 Fla.). 



55974°— 35 2 



