TROPICAL NORTH AMERICAN SPECIES OF PANICUM. 
By A. 8. Hrrcscock and AGNES CHASE. 
INTRODUCTION. 
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 Leén 
of the Colegio de la Salle, 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 
1 Contr. U. 8S. Nat. Herb. 15. 1910. 
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