14 MISC. PUBLICATION 200, U. S. DEPT. OF AGRICULTURE 



So far as possible the names have been confirmed or identified by 

 examination of the types. The type of a species or variety is the 

 specimen which an author had chiefly in mind when he wrote the 

 original description. The type specimen determines the application 

 of the name. The type specimens of the early American botanists 

 are mostly in European herbaria. The types of species described by 

 Vasey and other botanists connected with the Department of Agricul- 

 ture are mostly in the United States National Herbarium. Types not 

 in Washington have been studied in other herbaria and photographs 

 and drawings made of them by the agrostologists of the Department 

 of Agriculture, or have been lent by the curators of the herbaria in 

 which they are deposited. Through the courtesy of these curators 

 many fragments of types have been deposited in the United States 

 National Herbarium. A few type specimens have not been located, 

 and doubtless in some of these cases there are no types in existence to 

 confirm original descriptions. A relatively small number of published 

 names still remain unidentifiable. These names are listed following 

 the synonymy. Certain exotic species, mentioned by horticultural 

 writers as being occasionally cultivated for ornament, have been 

 included in notes appended to the genera to which they belong. It 

 has not been practicable in all cases to verify the application of the 

 names on a type basis, and the species are admitted under the names 

 they bear in cultivation. 



COMMON NAMES 



The common or English names of plants are often uncertain in their 



application, different plants bearing the same name or the same plant 



bearing different names in different localities. A recent work, 



Standardized Plant Names, 3 has coordinated and standardized the 



common names. One of the authors of this work, Frederick V. 



Coville, has standardized the common names of the grasses for this 



manual. 



SCOPE OF THE MANUAL 



The manual includes descriptions of all grasses known to grow in 

 the continental United States, excluding Alaska. There are 159 

 numbered genera and 1,100 numbered species. Of these, 44 genera 

 and 151 species are introduced, mostly from the Eastern Hemisphere. 



In addition to the numbered species, which may be considered per- 

 manent constituents of the flora of the United States, there are a 

 number of species which are known only as ballast plants or as waifs 

 in the interior, or are only rarely cultivated. These appear not to be 

 established and are mentioned, without numbers, in paragraphs 

 appended to their nearest allies. They are not included in the keys. 



The manual is based mainly on the material in the United States 

 National Herbarium, the grass collection of which is the largest in 

 the world, numbering more than 210,000 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 information, 

 especially on the ranges of species. The cooperation of the Forest 

 Service, United States Department of Agriculture, has been invalu- 



3 American Joint Committee on Horticultural Nomenclature, standardized plant names. 

 Prepared by F. L. Olmsted, F. V. Coville, and H. P. Kelsey. 546 pp. Salem, Mass. 1923. 



