II EQUATORIAL VEGETATION 243 
whose trunks are formed by a miniature forest of aerial roots, 
sometimes separate, sometimes matted together, are charac- 
teristic of the Eastern tropics, but appear to be rare or alto- 
gether unknown in America, and can therefore hardly be 
included among the general characteristics of the equatorial 
zone. 
Besides the varieties of form, however, the tree-trunks of 
these forests present many peculiarities of colour and texture. 
The majority are rather smooth-barked, and many are of 
peculiar whitish, green, yellowish, or brown colours, or occa- 
sionally nearly black. Some are perfectly smooth, others 
deeply cracked and furrowed, while in a considerable number 
the bark splits off in flakes or hangs down in long fibrous 
ribands. Spined or prickly trunks (except of palms) are rare 
in the damp equatorial forests. Turning our gaze upwards 
from the stems to the foliage, we find two types of leaf not 
common in the temperate zone, although the great mass of 
the trees offer nothing very remarkable in this respect. 
First, we have many trees with large, thick, and glossy leaves, 
like those of the cherry-laurel or the magnolia, but even 
larger, smoother, and more symmetrical. The leaves of the 
Asiatic caoutchouc tree (Ficus elastica), so often cultivated in 
houses, is a type of this class, which has a very fine effect 
among the more ordinary-looking foliage. Contrasted with 
this is the fine pinnate foliage of some of the largest forest 
trees, which, seen far aloft against the sky, looks as delicate as 
that of the sensitive mimosa. 
Forest Trees of Low Growth 
The great trees we have hitherto been describing form, 
however, but a portion of the forest. Beneath their lofty 
canopy there often exists a second forest of moderate-sized 
trees, whose crowns, perhaps forty or fifty feet high, do not 
touch the lowermost branches of those above them. These 
are of course shade-loving trees, and their presence effectually 
prevents the growth of any young trees of the larger kinds, 
until, overcome by age and storms, some monarch of the 
forest falls down, and, carrying destruction in its fall, opens 
up a considerable space into which sun and air can penetrate. 
Then comes a race for existence among the seedlings of the 
