FORESTS OF PORTO RICO. 33 



gueros (not far from one-fourth the area of the island), as well as 

 Vieques, Culebra, Mona, and the other outlying islands. It still 

 occupies to a large extent the thin-soiled, rugged limestone hills, and 

 has extended itself on the poorer soils of the north coast, principally 

 at the expense of the dry tidal woodlands and moist deciduous forests 

 of the limestone formation. In both situations, however, its compo- 

 sition is somewhat modified through the persistence of some of the 

 more tenacious species of the formations displaced. On the deeper 

 soils of the more gentle slopes and plains of the south coast country 

 back from the streams the dry deciduous forest has in large meas- 

 ure been displaced by agriculture — nomadic agriculture originally 

 which burned and destroyed the forests and planted on their ashes. 

 This land once cleared and then abandoned reverts to a forest growth 

 with extreme difficulty, if at all. The open grass-covered savanna 

 is the general result, with but here and there a tree where a particu- 

 larly large individual escaped destruction or local conditions favored 

 its getting a start and enabled it to compete with the turf. A tran- 

 sitional form of forest which might be called the " savanna forest" 

 may occasionally be met with where the open savanna and the true 

 forest join. Here the most hardy and drought-resisting varieties of 

 trees form open stands in the grassy waste. 



Although the dry deciduous forests vary from the closed chaparral 

 form to that of the open savanna, they have certain well-defined 

 characteristics. They are more or less leafless during the several 

 months of the dry season and have a generally brown and parched 

 appearance, evergreen trees such as the pajuil (86) being rare. Grass 

 and other herbaceous growth under and between the trees is almost 

 always present. Lianas are small and slender and absent entirely 

 from the more open parts of the formation. Tillandsia (Spanish 

 moss) festoons many of the trees and is the most conspicuous and 

 most common among the epiphytes, here known collectively as 

 pinuelas. There are a few other bromeliads and an occasional orchid. 

 Exceedingly characteristic also of the formation are the pitajaya 

 (120) and tuna (120), the tree cactuses and opuntias. 



The trees themselves, rarely over 30 feet high, are short and thick- 

 bodied, have a thick, fissured bark and a light, open, feathery crown 

 which in the open is very apt to be flat-topped and umbrella-shaped, 

 or to have its branches and foliage arranged in tiers. Leguminous 

 trees with thorny branches and fine, usually firm-textured compound 

 leaves, are particularly characteristic. Among the more common of 

 these are guava (36), guama (37), tachuelo (54), cobana negra (44), 

 algarrobo (45), campeche (50), moca (58), and many others. The 

 wood of many of these trees is extremely heavy, hard, and durable. 

 21871°— Bull. 354—16 3 



