22 Aij:xandf.r G. R(;tiivi;x 



tion is similar to that around Riohacha until the Rio Camarones is reached 

 at Barbacoas, and where the foothills begin. The flood-plain of the river 

 here is very wide in places and heavily timbered with massive trees, inter- 

 mingled with dense undergrowth, while the low hills are covered with the 

 semi-arid type of low woodland, abounding in shrubbery and small trees, 

 the whole region showing the effect of a very low humidity. After leaving 

 Barbacoas the trail soon begins to wind up into the foothills of the great 

 northeast spur-range. The forest becomes heavier and heavier, with less 

 and less undergrowth, until at an elevation of perhaps 3,000 feet the forest 

 is composed entirely of tall, massive trees, with little or no undergrowth. 

 This forest undoubted!}^ extends westward unbroken over the whole north- 

 ern flank of the Sierras. The trail crosses the range at an elevation of 

 approximately 5,000 feet, then descends to the Rio Rancheria above Fon- 

 seca. The heavy forest of the north slopes extends unbroken up to the 

 crest of the divide and slightly over it, but there is an almost instantaneous 

 change after crossing the crest ; the dense forest of large trees gives way to 

 an open wodland of small trees and tangled underbrush, even the species 

 changing almost entirely. 



Descending the slope, the woodland becomes sparser, acacia-like forms 

 and cacti soon appear, and there are tracts of open savanna. Lower in the 

 foothills and upper parts of the valley we have again the same vegetation 

 as along the trail between Riohacha and Barbacoas. The flood-plain of 

 the Rio Rancheria is heavily forested, like that of the Camarones at Bar- 

 bacoas, except in the vicinity of Fonseca, where it has been deforested. 

 However, as elsewhere noted, these forests of the river flood plains derive 

 their moisture more from the subsoil rather than from the rainfall. From 

 Fonseca to San Juan de Cesar the trail is close to the base of the foothills 

 over a cactus- and acacia-covered plain, and the height of land separating 

 the basins of the Rio Rancheria and the Rio Cesar is so inconsiderable that 

 it is scarcely noticeable as one crosses it. There is but one small stream 

 descending from the foothills between Fonseca and San Juan, and this was 

 dry when we crossed it. The adjacent foothills are either sparsely clothed 

 with low scrub or grass, or are bare and rocky slopes. 



From San Juan de' Cesar to Valle de Upar the vegetation is practically 

 the same, except for the forests of the Badilla River flood-plain, which is 

 very broad and well wooded. The acacia-like shrubs and trees and cacti 

 abound everywhere else, with some slight approach to savannas in places, 

 especially near Badilla and above the flood-plain of the Rio Guatipuri. The 

 flood-plain of the "Guatipuri is very extensive as one approaches Valle de 

 Upar, with many canals and irrigation ditches, but on the south side of the 

 river the land is higher and the arid woodland is largely in evidence. This 

 same condition continues southward (at least along the trail) for about five 

 miles, except that cacti and acacias are less abundant and other species of 

 trees and shrubs begin to appear, and then the dry woodland changes grad- 

 ually into a fairly heavy flood-plain forest Avhich extends southwestward, 

 with but few breaks, to a point some ten miles south of Valencia de Jesus. 

 This is, in greater part, a magnificent lowland forest, consisting of many 



