VI PREFACE, 
and the northern part of South America, hitherto imperfectly or 
not at all known. Most of them are components of the wonder- 
fully rich native Isthmian silva and several aro of importance as 
timber trees. <A large part of the paper is devoted to a revision of 
the genera Brownea and Browneopsis founded on the extensive ma- 
terial collected by the author in Darien and Venezuela. Mr. Pit- 
tier’s recent observations and collections in Panama permit a better 
understanding of the genera Bombax and Pachira, which has led 
him to segregate two species from Pachira to form the new genus 
Bombacopsis. 
Part 5 consists of a paper by Mr. Pittier dealing with Inga, a very 
large American genus of leguminous trees. In identifying recent 
Panama material Mr. Pitticr found it necessary to undertake a critical 
review of all the species of the genus. No gencral treatment of Inga 
has appeared since Bentham’s extensive monograph in 1875, although 
many species have been described since that year. For several rea- 
sons a conclusive revision of the genus is impracticable at the present 
time. Many of Mr. Pittier’s conclusions, however, are embodied in 
this paper, which consists chiefly of critical observations upon the 
characters and status of some of the older species, notes on their 
arrangement in a natural classification, and descriptions of new 
Species as represented by specimens in several of the larger American 
herbaria. There is given, in conclusion, a list of all the species 
deemed valid, with an indication of those lacking in the American 
herbaria consulted. 
In part 6, which is the sixth installment of his serics on Central 
American and Colombian plants, Mr. Pittier puts on record further 
results of his work. All the species treated are trees or shrubs, and 
most of them are here described for the first time. One of the new 
Species, Afimusops darienensis, is the tree which yields the Panama 
“balata” or gutta-percha, a very important commercial product. 
Hitherto this tree has been confused with another species of Mimu- 
sops, from British Guiana. 
The last and longest paper (part 7), by A. S. Hitchcock, Systematic 
Agrostologist of the United States Department of Agriculture, and 
Agnes Chase, Assistant Agrostologist, brings together in a single 
convenient publication our knowledge of the grass flora of the West 
Indian Islands. Though some of the earliest collections of plants 
sent from America to Europe came from the West Indies, and though 
the flora of this region has since been studied by many botanists, no 
account of the grasses of the whole region has hitherto been published. 
The present paper is based upon large collections from practically all 
the islands of the group and upon field studies by both authors. It 
includes 110 genera and 455 species, of which 1 genus and 17 species 
