TROPICAL NORTH AMERICAN SPECIES OF PANICUM. 



By A/S. Hitchcock and Agne>s Oh\se. 



INTEODUCTIOF. 



In a preceding paper ^ our knowledge of the North American species 

 of Panicum was presented in a revision of the genus, based upon mate- 

 rial in the United States National Herbarium. Since the publication 

 of that paper a large amount of additional material from tropical 

 North America has been accumulated. Mr. Hitchcock visited Mexico 

 in 1910, Central America and Panama in 1911, and Jamaica and Trini- 

 dad in 1912. Mrs. Chase visited Sonora in 1910 and Porto Rico in 

 1913. The collections of Mr. H. Pittier in Panama, of Brother Leon 

 of the Colegio de la SaUe, Habana, in Cuba, and of several other col- 

 lectors in tropical North America, besides specimens from various 

 islands of the West Indies received through Dr. I. Urban, serve to 

 augment the amount of material studied. As a result of these further 

 studies in the genus the range of nearly all the tropical species 

 described in the revision can be presented in much greater detail. 

 Several South American species hitherto unknown from North 

 America and several new species have been discovered, while a few 

 doubtful species and a few referred to synonymy have by field work 

 and further study been established as valid. 



While the present paper is supplementary to the revision, it is 

 designed to be of use for the region covered without necessarily 

 referring to the main work. For this reason keys are given for all 

 the tropical species, though descriptions are given of additional species 

 only. A study in their native habitat of species before known from 

 herbarium specimens alone, has necessitated in some cases a revision 

 of the description of habit or of duration, or exceptions have been 

 found to characters given as common for groups. Such notes are 

 given without other description and are to be understood as additions 

 to or corrections of the descriptions given in the revision. Following 

 the reference to the original publication of each species is a reference 



' Contr. U. S. Nat. Herb. 15. 1910. 



459 



