50 THE HUMAN SIDE OF PLANTS 
holding. To this end the inner walls of the cacti 
are filled with sponges which can absorb immense 
quantities of water. The roots travel great dis- 
tances into the earth to take up the moisture. This 
is one of the reasons for the coating of daggers 
and hooks which cover every part of the cacti. 
Without these weapons they would be destroyed 
by the hungry and thirsty animal life of the desert. 
The cocoanut has been forced by many hard 
knocks to learn to defend itself not only against in- 
clement weather but also against salt water. The 
cocoanut grows in the tropics and usually near the 
shores, where it has been planted by the tides. 
Here new plants spring up; and because they grow 
beside the sea and the probability is that the fruit 
will fall into the water, the plant has provided for 
this emergency. In the first place there is the long, 
fibrous covering of the nut, which prevents the 
salt water from entering and spoiling the fruit; 
then there is the impenetrable shell, a strong pro- 
tection against most forms of animal life. Also, 
the nut is of such shape that it floats very readily, 
and it is not unusual to see two or three cocoa- 
nuts drifting to a distant island or shore, as chil- 
dren run to new playgrounds. 
There are some plants which seek protection 
from adverse weather in sheltered spots. Such are 
