16 



FOREST CONDITIONS OF PORTO RICO. 



being of the open-textured white limestone type which abounds from 

 Florida southward, but is not common in the United States. 



The mountain areas present but little if any barren indurated rock 

 surface, but are covered with a deep red soil, to which vegetation clings 

 tenaciously. This mountain soil is one of the most marked features 

 of the island, and to it are largely due many of its agricultural and 

 forest conditions. Were it less tenacious and sticky than it is (and 

 language can hardly convey an idea of the unctuousness of this sticki- 

 ness, which is especially disagreeable in a road material) the mountain 

 slopes of Porto Eico would now be washed and dreary wastes of bar- 

 ren rock. This mountain soil is mostly red ferruginous clay, accom- 

 panied by much pebble and other rock debris. It resembles in color 

 and tenacity the red clay regions of the southern Appalachians, but is 

 derived from quite different rocks, and is apparently much richer in 

 phosphates and lime. These mountain soils are the residuum of the 



Subsoil and undergrowth in mountain regioi 



black basic volcanic rocks, the red color being derived from the iron 

 of the latter and the clay from its feldspars. The small patches of hard 

 limestone within the red clay area of the mountain region are usually 

 black, rich, and mellow, and are much more fertile. This is especially 

 notable in the tobacco region around Cayey, which is confined to soils 

 of this character. -This soil is naturally ameliorated by the vast 

 amount of humus derived from the native vegetation. (See fig. 4.) 

 Decay is so rapid under perpetual warmth and moisture that the vol- 

 canic rocks quickly rot and weather into soils of this character. The 

 regolith or decayed superfice of the rocks is unusually deep on these 

 mountains, extending down 50 or 100 feet, correspondingly affording 

 a splendid medium for root hold and penetration. 



Owing to this soil the mountains were originally wooded and are now 

 cultivated to their very summits, vertically of slope presenting no 

 obstacle to cultivation in the minds of the natives. The writer has 



