TROPICAL ZONE 
189 
IV. Tropical Zone \ This includes most of the land 
between the tropics, wherever the rainfall is sufficient to 
prevent the formation of deserts. It passes gradually into 
the desert regions of the preceding and the succeeding 
zones. There is no interruption of vegetation by cold, but 
in most of the continental parts, excepting the extreme north 
of Australia, south of India, western equatorial Africa, and 
the Amazon valley, there is a dry season of at least three 
months in summer which necessitates a xerophytic character 
in the vegetation. Part of these drier regions is covered 
with forest ; often many of the trees have deciduous leaves, 
e.g. in the ‘ Catinga ’ forests of Brazil. Lianes are less 
common than in the wet regions described below, epiphytes 
are few and of the most xerophytic kinds. Cacti, Euphor- 
bias and other xerophytes are common in many parts, and 
with a few Acacias, &c., may represent the copse vegetation 
of this zone. Large open areas occur, covered with grasses 
(Chlorideae, Festuceae, &c.), among which many flowering 
herbs and undershrubs often occur. In most places these 
areas are interrupted by patches of copse or forest, and are 
then termed savannahs (America) or park-lands . 
In the more strictly equatorial regions, i.e. in western 
equatorial Africa, the extreme south of India, the Amazon 
valley, the extreme north of Australia, and in the islands, 
e.g. southern Ceylon, the Malay Archipelago, &c., there is 
rain at almost all periods of the year, and especially at the 
two seasons when the sun has just passed overhead. Here, 
tropical vegetation is seen in its highest development. The 
air is constantly warm and moist, the range of temperature 
is small, there are no extremes of dryness, and everything 
favours rapid and luxuriant growth. 
The bulk of the lowland area is (or was formerly) covered 
1 Schimper, Warming, &c., op. cit.\ Darwin, Naturalist's Voyage ; 
Wallace, Malay Archipelago, Island Life, Tropical Nature, Naturalist 
on the Amazon ; Rod way, In the Guiana Forest ; Kurz, Report on the 
Forest and other Vegetation of Pegu, Calcutta, 1876; Haberlandt, Eine 
Botanische Tropenreise ; Pearson, Botany of the Ceylon Patanas, Journ. 
Linn. Soc. xxxiv, 1899, p. 300; Willis and Gardiner in Ann. Perad. 
I. 1901 (shore plants); Keeble in Ann. of Bot. 1895 (hanging foliage) ; 
Stahl in Ann. Buitenz. 1893 (leaf form) ; Potter in Journ. Linn. Soc., 
1888 (bud protection); and cf. Climbers, Epiphytes, Halophytes, &c., 
above. 
