MEXICAN GRASSES IN THE UNITED STATES NATIONAL 
HERBARIUM. 
By A. S. Hrrcucock 
INTRODUCTION. 
The following list of grasses, based entirely upon specimens in the 
United States National Herbarium, is a preliminary paper, in which 
the scattered data upon Mexican grasses have been brought together 
and arranged in a convenient form. The species included have been 
accepted, for the most part, in their traditional sense. It has been 
impracticable to examine the types of many of the earlier described 
species since these specimens are located in European herbaria. 
For this reason the synonymy has been confined mostly to those 
names that could be fixed by an examination of American types, or 
concerning the application of which there was little doubt. The 
largest number of unidentified names are found in Fournier’s work 
on Mexican grasses.! This results from the incomplete or unsatis- 
factory descriptions and from the fact that the specimens cited 
under a given species either may not agree with the diagnosis, or may 
belong to two or more species, at least in different herbaria. An 
examination of the original specimens will undoubtedly lead to the 
identification of the greater part of these names. 
There are several specimens that have been omitted from the list 
because they have not been identified and are apparently unde- 
scribed species. They belong to genera, however, that are much in 
need of critical revision and further study of them is deferred for the 
present. In subsequent articles it is hoped to work out the classifi- 
cation of the tropical American grasses upon a type basis 
KEY TO THE GENERA. 
Spikelets with one perfect terminal floret, and usually 
a second staminate or neutral floret below 
(lower floret perfect in Isachne); rachilla ar- 
ticulated below the glumes, the spikelets fall- 
Fournier, Eug. Mexicanas Plantas. Pars secunda. Gramineae. 1886. Fordis- 
cussion of the date of publication of this work see Contr. U.S. Nat. Herb. 15: 49. 1910 
and op. cit. 14: 350. 1912. 
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