262 TROPICAL NATURE Il 
can be put to uses which, if ordinary wood were used, would 
require hours or even days of labour. There is also a regu- 
larity and a finish about it which is found in hardly any other 
woody plant; and its smooth and symmetrically ringed 
surface gives an appearance of fitness and beauty to its 
varied applications. On the whole, we may perhaps consider 
it as the greatest boon which nature gives to the natives of 
the eastern tropics. 
Mangroves 
Among the forms of plants which are sure to attract 
attention in the tropics are the mangroves, which grow 
between tide-marks on coasts and estuaries. These are low 
trees with widely-spreading branches and a network of aerial 
roots a few feet above the ground ; but their most remarkable 
peculiarity is, that their fruits germinate on the tree, sending 
out roots and branches before falling into the muddy soil— 
a completely formed plant. In some cases the root reaches 
the ground before the seed above falls off. These trees 
greatly aid the formation of new land, as the mass of aerial 
roots which arch out from the stem to a considerable distance 
collects mud and floating refuse, and so raises and consoli- 
dates the shore ; while the young plants, often dropping from 
the farthest extremity of the branches, rapidly extend the 
domain of vegetation to the farthest possible limits. The 
branches, too, send down slender roots like those of the 
banyan, and become independent trees. Thus a complete 
woody labyrinth is formed ; and the network of tough roots 
and stems resists the action of the tides, and enables the 
mud brought down by great tropical rivers to be converted 
into solid land far more rapidly than it could be without 
this aid. 
Sensitive Plants 
Among the more humble forms of vegetation that attract 
the traveller's notice none are more interesting than the 
sensitive species of Mimosa. These are almost all natives of 
South America, but one species, Mimosa pudica, has spread 
to Africa and Asia, so that sensitive plants now abound as 
wayside weeds in many parts both of the eastern and west- 
ern tropics, sometimes completely carpeting the ground with 
