PREFACE. 
In the act of Congress making appropriation for the Department 
of Agriculture for the fiscal year ending June 30, 1889, provision was 
made for botanical exploration and the collecting of plants in little 
known districts of America. The results of the work carried on 
under this and later appropriations for similar purposes, both in the 
Department of Agriculture and in the N ational Museum, have been 
published from time to time in the Contributions from the United 
States National Herbarium. 
Two of these papers included in the present volume are a continu- 
ation of the researches of Dr. J. N. Rose on the flora of Mexico, a 
partial result of his third and fourth journeys to that country, which 
have enabled him to supplement his critical herbarium studies by 
valuable field observations. Throughout the progress of the work 
the scientific value of this field experience has been manifest and the 
wisdom of the Museum’s policy of giving the critical student oppor- 
tunities of this kind has been fully confirmed. 
The extension of American jurisdiction over Porto Rico and the 
Philippine Islands in the year 1898 created a demand for information 
regarding the plants of those islands. Both areas contained a tropical 
flora, and American botanists had devoted little attention to the 
study of tropical plants. The information demanded regarding the 
Porto Rican flora was largely of a popular and commercial character 
and was not at all to be satisfied by the existing and available tech- 
nieal works on the West Indian flora. In the course of their investi- 
gations on tropical agricultural plants in Porto Rico, Mr. Cook and 
Mr. Collins collated a large amount of information on the economic 
plants of that island such as was not suitable for incorporation in 
their detailed reports on staple and special agricultural plants, which 
are published by the United States Department of Agriculture. This 
information has been brought together in the paper on Economic 
Plants of Porto Rico, included in this volume. Fortunately the 
plant names in use among the people of Porto Rico are applied with 
approximate precision, so that by adding the botanical identification 
of a plant to its Porto Rican popular name we have in most Instances 
a direct key to its botanical name and position. Furthermore, the 
use of illustrations reproduced from good photographs conveys ina 
simple and direct way information which no amount of technical 
description could replace. 
Freperick V. CoviILuEe, 
Curator of the United States National Herbarium. 
Vv 
