NATURAL AREAS AND REGIONS 



areas, correponding to those of greater 

 atmospheric precipitation. In the low- 

 lands, they attain imposing proportions. 

 The pillar-like trunks of the trees rise 

 to 30 or 40 meters before spreading in a 

 dome of dense foliage, which is in it- 

 self a real plant kingdom, such is the 

 wealth of epiphytes, parasites and vines 

 established upon it. Only a very at- 

 tenuated light passes through the thick 

 foliage but nevertheless, a wonderful 

 storied vegetation fills the space under 

 the larger trees, the lowest tier of which 

 completely hides the rich soil. This is 

 formed by layer upon layer of the decay 

 of past plant generations, and is so soft 

 that the giant trees can maintain their 

 equilibrium only by special adaptations. 

 These are, for instance, plank-but- 

 tresses, as in the case of Ceiba pentandra, 

 or adventitious roots such as those of 

 Cecropia and Iriartea. 



Great is the variety of vines which 

 form a distinguishing trait of these rain 

 forests. Some originate high up on the 

 branches of the trees and their aerial 

 roots, stretched down into the soil, 

 look taut cordage. Others creep along 

 the tree-trunks, which they partially 

 conceal under their beautiful foliage, 

 while still others climb independently, 

 as they may, helping themselves with 

 aculei, tendrils, twists or other peculiar 

 modifications, until they reach the bril- 

 liant sunlight above. We have already 

 mentioned the epiphytes, Aroids, Bro- 

 meliads, Orchids and others. Palms, 

 belonging to the genera Jessenia, Eu- 

 terpe, Martinezia, Manicaria, Astro- 

 caryum and others, found also in the 

 monsoon forests, either fill part of the 

 space under the larger trees, or pierce 

 through the leafy dome. 



Among the numerous species of trees 

 which form the tropical forests, the 

 following are either more conspicuous, 

 or better known on account of their 

 economical uses: In the Orinoco Delta 

 and surrounding region, we have forest 

 giants like Dimorphandra excelsa, Nect- 

 andra Rodiei, Virola venezuelensis, along 

 with the ever-recurring Ceiba pentandra, 

 several Ficus species, and others of 



lesser proportions, among which Sym- 

 phonia globulifera and Carapa guianen- 

 sis are also worthy of mention. The 

 Upper Orinoco and Rio Negro district, 

 relatively well known, thanks to the 

 explorations of Spruce, are especially 

 rich in species of Licania, Swartzia, 

 Hirtella, Ouratea, Macrolobium and Vi- 

 rola, and certain genera of palms, such 

 as Bactris, Mauritia, Astrocaryum and 

 Lepidocaryum, seem to reach their 

 fullest development in this region. The 

 flora of the rain forest of the Maracaibo 

 basin is no less diversified; besides 

 Copaifera Langsdorffii, found through- 

 out the region, we may cite C.fissicuspis, 

 Cariniana pyriformis, Goupia glabra, 

 Dialium divaricatum, Gustavia fustis- 

 mortui, Labatia parviflora, as well as 

 at least two cow-trees, Couma sapida 

 and Zschokkea edulis. Here, the palms 

 seem to belong principally to the genera 

 Jessenia, Bactris and Attalea. 



Floodplain Forest (H. B. .). In the 

 preceding description, Dr. Pittier has 

 mainly described the lowland type of 

 forest in Venezuela, which has been 

 mapped by W. Sievers (1896; Petermanns 

 Mitteilungen, vol. XIII, pi. XV). My 

 own observations lead me to believe that 

 this is not entirely a rain-forest, de- 

 pendent on the precipitation, but 

 largely an edaphic one, more closely 

 related to the amount of soil water. 



Throughout Venezuela, one is im- 

 pressed by the abundant evidence that 

 the volume of water in the streams must 

 vary greatly with the seasons. Many 

 of the larger rivers, like the Rio Cata- 

 tumbo throughout its lower course, 

 have, by repeated floods, built up their 

 banks higher than the surrounding 

 country, so that the surface drainage, 

 during the dry season, is away from, or 

 parallel to, the main stream. On these 

 flood plains, the smaller streams, during 

 the dry season, either meander through 

 gravel bars, between high, vertical 

 banks, or disappear in the sand of 

 numerous, anastamosing channels, 

 which may retain long, stagnant pools 

 (canos, or sewers) or lead into large, 

 shallow lakes (cienagas). As a result, 



