26 BULLETIN 354, U. S. DEPARTMENT OF AGRICULTURE. 



veloped on the south. Here it occurs chiefly at the mouths of the 

 larger rivers, where a dilution of the sea water enables it to grow 

 in spite of the otherwise unfavorable climatic conditions. 



Three of the four common species of the western mangrove, 1 of 

 tropical American and West African coasts, occur in Porto Rico. 

 One is known locally as mangle Colorado (122), 2 and the other two 

 as mangle bianco (or bobo) (127 and 157). Mangle Colorado occupies 

 the outer exposed edge of the formation, while mangle bianco occur, 

 the one (Avicennia) intermediately and the other (Laguncularia) at 

 the inner boundary. The latter often forms pure mangrove. Other 

 species associated with this formation are mangle boton (125) and 

 mangle prieto (unidentified), small trees, usually under 20 feet in 

 height. On drier islets within the formation other species may occur, 

 and likewise on the inner side, where by a gradual transition the man- 

 grove gives way to the dry tidal woodlands. Epiphytes, so charac- 

 teristic of other tropical forest formations, are scarce and are con- 

 fined to a few bromeliads and lichens. 



The mangrove is of considerable economic importance, furnishing 

 fuel, especially to the bakeries, from its limbs and branches, and posts 

 and house piling from the submerged parts. For these latter uses it 

 is very highly prized because of its resistance to decay and to the 

 attack of the white ant. The bark contains a tanning material and 

 a dye, though to what extent it is used locally is not known. 



Practically all of this mangrove land belongs to the insular govern- 

 ment. In a few places, as in parts of San Juan Harbor, the mangrove 

 will have to be cleared away to make room for needed water-front 

 improvements. Other tracts might perhaps be converted into arable 

 land by drainage. Most of these lands, however, should be retained 

 by the government and managed under approved forestry principles 

 as public wood reserves. 3 They would constitute a most valuable 



iThe fourth species, Avicennia tomentosa Jacq., is not identified from Porto Rico. The eastern man- 

 grove is much richer in forms. Thus in Farther India and the Malay Archipelago, where it shows its 

 greatest diversity, it consists of Rhizophoracea? (9 species), Lythraeeae (3 species), Combreteceae, Meliaceae, 

 and Verbenaceae (2 species each), Myrisinacese, Rubiacese, Anthraceae, and Palmae (1 species each); 22 

 species in all, according to Schimper. 



2 The figures in parenthesis refer to the descriptive list (Appendix I). 



8 In many eastern tropical countries the immense value of these swamp areas is now fully appreciated. 

 In the Federated Malay States the mangrove is classed as "one of the two important divisions of the com- 

 mercial Malay forests.'' In 1904 the development of the mangrove areas as a source of fuel supply for the 

 Government railways and for general public consumption was begun under sytematically prepared working 

 plans. (Burns- Murdock, A. M. "Notes from the Federated Malay States," Indian Forester, Vol. XXX, 

 No. 10, Oct., 1904). 



In the Philippines the mangrove is regarded as "in many respects one of the most valuable forest assets 

 of the islands." The bureau is now engaged in selecting the most important commercial areas and thor- 

 oughly investigating their possibilities. (Director of Forestry of the Philippine Islands, annual report 

 for fiscal year ending June 30, 1912). 



The mangrove is managed on a short rotation under a clean-cutting system, making it a simple crop 

 to handle. As practiced by the Philippine natives in growing "bacauan" (includes several mangrove 

 species) for cordwood, the seed is collected and sown at a cost of about S2.50 an acre. Then without any 

 further attention the crop at the end of six years is ripe to cut, and brings as high as S20 an acre on the 

 stump, according to W. D. Sterrett, formerly forester of Bataan Province, Philippine Bureau of Forestry. 



