26 AMAZONIA AND LA PLATA. 



dense haze like rocky islets in the midst of the sea. The plains, the headland-^, 

 everythino- is wrapped in this damp covering, with which are intermingled the 

 miasmatic exhalations of the soil. On the Tumuc-Humac Mountains, where in 

 the space of five months Coudreau made over fifteen hundred observations, the 

 atmosphere is less charged with moisture than on the coastland;^. " Here the 

 foo-s are drier, and the night temperature falls to 16 degrees " (61° Fahr.).* 



Flora of the G lianas. 



To the irregular distribution of the rainfall must be attributed the striking 

 contrasts presented by the flora of the Guianas, There are two distinct botanical 

 zones — the savannas, or campos, as the Brazilians call them, and the primeval 

 woodlands. But account must also be taken of various sandy and arid tracts 

 destitute of all vegetable humus, and of other districts, where, despite the 

 moisture, arborescent plants are prevented from springing up by the dense forests 

 of reeds. 



The treele-s regions extend for the most part below the hills or mountains, 

 whose upper flanks are exposed to constant rains. Thus in British Guiana tbe 

 upper Takutu basin, sheltered from the moist winds by the eastern offshoots of the 

 Pacaraima rano-e, lies altogether within the zone of savannas. But certain plains 

 in close proximity to the Atlantic coast are completely destitute of forest growths, 

 althouf^h in their geographical position and absence of relief they closely resemble 

 other well-wooded plains. Thus in the contested Franco-Brazilian territory the 

 savannas, interrupted only by fiinges of trees along the river banks, extend 

 parallel with the Atlantic coast all the way from Cape Orange to the Amazons 

 estuary, and nearly the whole of the lower Araguari valley forms a vast treeless 

 carapo. 



In British and Dutch Guiana, the savannas form a narrow belt of open 

 ground reaching from the banks of the Demerara to those of the Surinam. The 

 existence of these treeless tracts between the mangrove- covered littoral and the in- 

 land forests is due partly to a local disturbance of the moist winds, partly to the 

 nature of the soil, formerly the bed of a lake. 



Like the Venezuelan llanos, the savannas of Guiana present the whole series 

 of transitions from a wooded to a grassy surface. In some districts the limits of 

 the different zones are as sharply defined as those of land and sea formed by 

 vertical cliffs. On emerging from the virgin forest with its tangle of lianas and 

 parasites, the wayfarer suddenly finds himself surrounded by a sea of herbaceous 

 growths, where the eye sweeps unhindered over a vast horizon limited in the dis- 

 tance by a sky-line of mountain crests. Elsewhere the woodlands break into an 

 irregular fringe of glades, distribute their trees more openly, and lower their 

 height, scattering clusters of wooded islets round about their verge. 



* Meteorological conditions of the Guiana seabosrd : — 



Mean Highest Lowest Painy 



Temperature. Temperature. Temperature. Days. EainfaU. 



Georgetown . ST E. 90" F. 74° F. 170 119 inche.s 



Paramaribo . 79° P6° 70° 177 HO ,, 



Cayenne . .80=" 92" 72' IbO 130 ,, 



