drawinjif and compariiifj the specimen with the 

 main distinpuisliing cliaracters or, if needed, with 

 tlie detailed description of leaves, flowers, and 

 fruits. Otherwise, the use of the same common 

 name for unrelated tree species in different places 

 or misapplication of a name may lead to confusion. 



The List of Tree Species with Descriptions and 

 Illustrations will also aid identification because it 

 lists the species in the usual botanical arrange- 

 ment with related trees together, alphabetically by 

 scientific names under each plant family. If the 

 family is recojjnized, names of the examples with 

 pap:e numbers will be found in the List. Likewise, 

 an unknown tree resemblinfi a known one should 

 be sought in the same family. 



The Key to Families serves to place an iniknown 

 tree in its plant family. This key includes the 68 

 families of this book and 20 additional small fami- 

 lies represented by only a few native tree species. 

 Each family with two or more species illustrated 

 contains a key to these species for further identifi- 

 cation. 



The Special Lists may be helpful also in identi- 

 fying trees with unusual characters or special uses. 



For trees not included, reference may be made 

 to Britton and Wilson's (5) flora of Puerto Rico 

 and the Virgin Islands, which contains both keys 

 to species and botanical descriptions. Also bo- 

 tanical specimens of dried pressed twigs with 

 leaves, flower.s, and fruits, and with field notes (lo- 

 cality, altitude, date, common name, collector, 

 whether wild or planted, size, abundance, etc.) 

 may be forwarded to large herbaria or universi- 

 ties for identification by specialists. 



STATISTICAL SUMMARY 



The 250 species of common trees of Puerto 

 Rico and the Virgin Islands described and illus- 

 trated here are classified into 185 genera and 68 

 plant families. Of these, 72 species, 38 genera, 

 and 6 families are exotic, or introduced. These 

 genera and families are not represented also by 

 native species of trees or smaller plants. For fur- 

 ther identification the 130 additional, related tree 

 species (including 10 introduced) of the same gen- 

 era are mentioned briefly and compared with 

 those illustrated. Thus, 380 tree species are in- 

 cluded for identification. To account for all native 

 tree s]iecies recorded by Britton and Wilson (5) in 

 these genera, 22 additional species of Eugenia ancl 

 15 of Mironin are listed. A second volume is 

 planned to describe and illustrate the remaining 

 native tree species and widely grown exotics in 

 these and other genera and in 20 other families. 



Numbers of tree species accepted for an area will 

 depend upon the definition of a tree or minimum 

 size considered. Trees may be defined as woody 

 plants having one erect perennial stem or trunk 

 at least 3 inches (7.5 centimeters) in diameter at 

 breast height (d.b.h. or at 41/2 feet or l.-l meters), 

 a more or less definitely formed crown of foliage, 

 and a height of at le;ist 12 to 15 feet (4 meters). 



Accordingly, some small trees often shrubby and 

 not reaching sawlog size have been included. 



ACKNOWLEDGMENTS 



^ Credit is due various persons of the United 

 States Forest Sei-vice, past and present, for their 

 assistaiice in preparing this book and particularly 

 to Leslie R. Holdridge, who initiated the project, 

 made extensive botanical collections, supervised 

 drawing of numerous illustrations (also making 

 a few), and wrote the two preliminary volumes. 

 In those volumes acknowledgment was made to 

 assistance in the preparation of the material by 

 personnel of Work Projects Administration Offi- 

 cial Project No. 165-2-36-20. 



Most of the black and white drawings were pre- 

 pared some years ago by several artists employed 

 by the United States Forest Service and Work 

 Projects Administration. Francisco Roena Santi- 

 ago made more than 50 of these. In 1954 to com- 

 plete this volume about 50 drawings were made by 

 Edwin C. Rivera S. and 10 by Felix Rosado. Five 

 others were prepared for a similar book on the 

 common trees of Venezuela by the senior author. 

 They are f'eiha- pentandm. TermirmUa cafappa, 

 and Tecoma stems by Ruby Rice Little and Cono- 

 carpus ererfiis and Aricennia nitida by Ellen de 

 Jiirgenson. The drawing of Necfandra cormcea 

 was made by Jane W. Roller. 



Assistance of the New York Botanical Garden 

 in making determinations of the earlier botanical 

 collections is appreciated. Acknowledgment is 

 due the United States National Museum for the 

 privilege of examining the large Puerto Rican 

 and Virgin Islands collections in the National 

 Herbarium. 



Foresters, rangers, and others of both the 

 United States Forest Service and Commonwealth 

 Division of Forests, Fisheries, and Wildlife have 

 assisted the authors in field work and in checking 

 the common names. The authors are deeply in- 

 debted to Jose Marrero, of the Institute of Tropi- 

 cal Forestry and coauthor of the Spanish edition 

 (21), for his review of the manuscript and for his 

 Spanish translation. Credit is due Franklin R. 

 Longwood of the United States Forest Service, 

 for the detailed data on about 60 Puerto Rican 

 woods taken from his publications which appeared 

 while this manuscript was awaiting publication. 



Distribution data by municipalities were com- 

 piled from the forest inventory of Puerto Rico, 

 which was conducted by the Commonwealth Divi- 

 sion of Forests, Fisheries, and Wildlife under the 

 direction of Benjamin R. Seda. From these rec- 

 ords the distribution maps were made by Raul 

 Ybarra C, of the Institute of Tropical Forestry. 



Alfonse Nelthropp, of Charlotte Amalie, St. 

 Thomas, has contributed many common names 

 used in the Virgin Islands. Roy O. Woodbury, 

 of the University of Puerto Rico Agricultural 

 Experiment Station, has checked and added to the 

 list of species growing also in southern Florida. 



11 



