My intention in preparing the present work has been to bring together, for the guidance of those who live in the tropical and subtropical regions of the globe, the available information concerning the principal fruits cultivated, or which may be cultivated, in those regions. The banana, the coconut, the pineapple, the citrus fruits, the olive, and the fig are not included, however, since these have been fully treated by other writers. Nor have I attempted to describe all of the fruit-bearing plants of the tropics: rather has it been my aim to concentrate on those which most seem to merit extensive cultivation, the culture of many of which is as yet little understood. No work in the English language has attempted to cover this subject, and the few which have appeared in other languages do not contain the data concerning propagation and cultural practices which would make them useful to horticulturists. Unfortunately, as regards many of the less-known fruits, few data are available, but concerning the more important ones the researches of such workers as E. Bonavia, A. C. Hartless, and William Burns in India, H. A. Van Hermann, F. S. Earle, and C. F. Kinman in the West Indies, George B. Cellon, Edward Simmonds, W. J. Krome, P. H. Rolfs, and Reasoner Brothers in southern Florida, F. Franceschi (E. O. Fenzi) and Ira J. Condit in California, J. E. Higgins and his associates in Hawaii, P. J. Wester in the Philippines, and L. Trabut in the Mediterranean region, have brought to light much valuable information. The work of such men as G. N. Collins, O. F. Cook, David Fairchild, W. E. Safford, and Walter T. Swingle, of the Bureau of Plant Industry, United States Department of Agriculture, has also added materially to our knowledge of the subject.

References throughout the book indicate the extent of my indebtedness to these and other investigators. In order that the work may reflect as fully as possible the total knowledge at present available on any topic, I have drawn freely from all sources, exercising, at the same time, all possible care to avoid perpetuating the more than numerous errors with which the literature of tropical fruits is burdened.

For the past seven years, during a large part of which time I have traveled as Agricultural Explorer for the United States Department of Agriculture, I have had exceptional opportunities for gathering, at first hand, information for this work. In the course of my journeys I have visited Hawaii, Japan, the Philippines, the Straits Settlements, India, Arabia, North Africa, Mexico, Guatemala, the West Indies, and Brazil. This field work has alternated with and been supplemented by practical experience with the cultural problems of tropical and subtropical fruit-growing in California and Florida. To those familiar with the thorough and exhaustive treatises which have been published on the northern fruits, however, the present work will no doubt appear superficial in character. Necessarily it is so. Present knowledge of the greater number of tropical fruits is superficial, and many years must pass before it will be possible for a thoroughly comprehensive treatise to be offered on any one of the species here considered, excepting possibly the date.

I have been assisted and encouraged in the preparation of this work by many persons. It is a particular pleasure to acknowledge my indebtedness to Charles Fuller Baker, now Dean of the College of Agriculture, University of the Philippines, under whose guidance I first took up work in tropical pomology, and whose boundless enthusiasm for tropical plants has been a constant inspiration to me; to F. Franceschi, formerly of Santa Barbara, California, who was one of the pioneers in the introduction and cultivation of tropical fruits in California; and above all, to my present chief, David Fair-child, and my colleagues in the Office of Foreign Seed and Plant Introduction of the Bureau of Plant Industry. To Dr. Fairchild America is indebted for many choice varieties of the mango, the date, and other tropical fruits which are now cultivated in the United States, and for his assistance and encouragement in my own investigations I owe him a debt of gratitude which I can never pay.

W. J. Krome of Homestead, Florida, has criticized the chapters on the avocado and mango, and added many notes of interest and value to the former. W. E. Safford of the Bureau of Plant Industry has revised the chapter on the an-nonaceous fruits, and Henry Pittier of the same Bureau that on the sapotaceous fruits. To my brother, Paul Popenoe, I am indebted for most of the chapter on the date. H. H. Hume of Florida has criticized the chapter on the kaki. J. N. Rose of the United States National Museum has furnished most of the data on the tuna and pitaya. Sidney F. Blake of the Bureau of Plant Industry has been of much assistance on matters of botanical nomenclature. J. Smeaton Chase of Palm Springs, California, has rendered valuable aid in the preparation of the manuscript. To all of these men I express my sincere appreciation of their help.

The line drawings with which this work is illustrated have been made by Mrs. R. E. Gamble of the Bureau of Plant In-dustry. Nearly all of them, as well as most of the half-tone plates, are from my own photographs; a few are from photographs by P. H. Dorsett of the Bureau of Plant Industry.

Wilson Popenoe

Washington, D. C,

October 1, 1919.