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NATURALIST'S GUIDE TO THE AMERICAS 



C; Desert 



To the xerophilous formations belong 

 also the half denuded rocks, met with at 

 all altitudes, exposed to the burning 

 sun and covered with a scant vegetation 

 of shrubs, herbs, mosses and lichens. 

 (The mesa tops, mentioned below, 

 are also practically sandy deserts, with 

 a sparse growth of Curatella americana; 

 Sievers maps the most extensive ones 

 in the northeastern portion of the 

 Orinoco valley — H. B. B.) 



d. Grassland 



1. Savanna. Although the Venezue- 

 lan savannas attain their greatest 

 development and diversity in the well- 

 known llanos, they exist on a limited 

 scale almost all over the country, 

 scattered through the forests and on 

 the mountain slopes. A small part of 

 them may have originated in the de- 

 struction of the forests by man, but with 

 these exceptions, they are certainly 

 the result of natural processes, and 

 maintain or lose their balance with the 

 wooded parts, either encroaching upon 

 them or giving way to them. They are 

 almost always bordered by a more or 

 less broad belt of low bush, which in 

 certain parts of the llanos is of the true 

 thorn-forest type. 



Contrary to the older descriptions, 

 the savannas are anything but uniform, 

 and the often pictured, boundless g; ass- 

 lands are only approximated away iu the 

 south, in the states of Portuguesa and 

 Zamora and beyond the Apure River. 

 These latter are the sabanas de matas 

 (grove savannas) of the natives, which 

 name indicates that even there the con- 

 tinuity of the grass surface is often 

 interrupted by masses of higher vege- 

 tation. Here the grass varies from a 

 low sward to the height of a mounted 

 rider. The rivers are barely outlined by 

 a fringe of low bush. In other sections, 

 an older level of the country, divided 

 by the erosion of the rivers, forms the 

 so-called mesas or table-lands, the arid, 

 sandy soil of which is sparsely covered 

 by a scanty, wind-barren vegetation. 



Although they are scattered all over 

 the llanos, these mesas belong to a 

 single complex. The rainwater which 

 they receive immediately filters through 

 the sand, to reappear at the foot, giving 

 origin to springs and streams, along 

 which extend by morichales, morass- 

 like areas with slow drainage. Upon 

 this inconsistent soil, extensive groves 

 of the palm {Mauritia flexuosa) rise from 

 a luxuriant tapestry of perennially 

 green vegetation, treacherous on ac- 

 count of the soft substratum. 



2. Grassland. The sabanas de pajo- 

 nales (straw or grass savannas) cover 

 here and there the slopes of the moun- 

 tains or hide in the middle of the for- 

 ests. With reference to the specific 

 composition of these distinct types of 

 savannas, we have as yet only very 

 scant information, with the exception, 

 of these pajonales of the coastal system 

 of mountains, which have been repeat- 

 edly explored. In their middle belt, 

 around Caracas, the dominating fami- 

 lies come in the following order: Grami- 

 nae (with Paspahim and Andropogon 

 (9 species each), Panicum (6 species), 

 Eragrostis and Sporobolus (4 species 

 each) as principal genera), Leguminosae 

 (Meibomia 11 species. Cassia 9 species, 

 Mimosa and Aeschynomene 4 species 

 each, etc.), Compositae and Cyper- 

 aceae. The forestal element is repre- 

 sented by dwarfed specimens of Roupala 

 and Byrsonima, together with a few 

 shrubby Myrtaceae. 



2. Fauna {H. B. B.). As Dr. Pittier 

 indicates, the larger portion of the 

 Venezuelan savannas are scattered with 

 groves of trees, in addition to the 

 swampy morichales and, of course, the 

 stream forest. In Venezuela, it is very 

 difficult to judge how much of the ap- 

 parent aridity is due to climate and 

 how much to deforestation. Most of 

 the northern region appears to become 

 savanna when the trees have been re- 

 peatedly burned away, and, outside of 

 the hills, practically none of the smaller 

 streams, even in the original forest, is 

 permanent throughout the year. In 

 this connection, it must be remembered 



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