Chap. Ill] TROPICAL WOODLAND AND GRASSLAND 277 



and also in moist depressions in the ground, in the same way as in the 

 campos. 



Only general facts are known regarding the climate of the llanos ; 

 accurate meteorological data are wanting. Yet, from the available material, 

 the climate may be described as one hostile to woodland. The year is 

 divided into a quite rainless dry season of five months, which is con- 

 temporaneous with our winter and early spring, and into a rainy season, 

 which begins at the end of April. In the climate of the llanos it is 

 the dry season that is hostile to woodland, for during the greater part of 

 its duration the dry easterly trade-wind blows almost continuously, and 

 usually with extreme intensity, and is associated with great heat and 

 excessive dryness of the air. 



A windy dry season is unfavourable to woodland, whereas it does no 

 harm to the thoroughly dried up prairie, whose existence is maintained 

 only in the subterranean parts of its plants, except when the season is 

 immoderately prolonged. Such abnormally long periods of drought are 

 not rare, but they are far more fatal to woodland than to grassland. 



In the llanos, according to Humboldt, it rains continuously during the 

 rainy season. This directly favours the prairie, whose existence, as we 

 know, depends more on very frequent showers than on heavy ones during 

 the vegetative season. 



The following extracts from Hann's ' Klimatologie ' give the character- 

 istics of the climate of the llanos : — 



' "The clearness of the air from December until February is incomparable. The sky 

 is continuously cloudless, and the presence of a single cloud is a phenomenon that 

 engages the attention of all the inhabitants. The wind blows strongly from the east 

 and north-east" (Humboldt). 



' C. Sachs stayed at Calabozo (9 N., 150 m. above sea-level) in the dry season (Dec. 

 1876 until Feb. 1877). He found a morning temperature of 22-25 C. before sunrise, 

 and 34-35 between 1 and 2 p.m. In February, the mean temperature between 1 and 

 2 p.m. is 35-9°, and the relative humidity 30%, and sometimes only 16%. The east 

 trade-wind blows constantly from sunrise until noon. Complete drought prevails 

 for five months, during which there is no dew. In April the rainy season begins, 

 and the land that has been parched into a desert becomes clothed once more with 

 dense vegetation ' (pp. 365-6). 



The small western islands of the West Indian archipelago are occupied 

 by woodland, which is favoured by the great humidity of the air. The 

 woodland is composed sometimes of rain-forest, as in Dominica, sometimes 

 of thorn-forest, as in St. Kitts, according as the rainfall is greater or less 

 than about 150 cm. 



I am personally acquainted with the vegetation of the two islands, regarding the 

 rainfall of which data are given below. The rainfall in Dominica, as I know from 

 experience, is considerably heavier in the mountains, where the high-forest shows 



