XVI 
CACTUS WATER BARRELS 
I SN’T IT ODD that plants which, in the beginning, 
came out of the water have learned, in some places, to 
live quite without it for months or even years! 
Take the members of the cactus family of the American 
Southwest, for instance. It is probably true that they 
have learned to live in drier places than any other of these 
plant children of the water. In Arizona, below the rim of 
mountains, lies the dry country, where the cacti have 
come to make their favorite home. 
These cacti are the camels of the plant world. They 
can go a long time without taking a drink. If they could 
not, they would not live long here. 
The cactus has learned to store water within itself and 
keep it there for extended periods, despite the fact that 
blazing sun and thirsty desert winds are always present 
and trying to drink it up. 
The barrel cactus furnishes a model example of water 
storage in the desert. It is as tall and nearly as big 
around as a flour barrel. It is armed on the outside with 
bristling thorns, which largely defend it from attack by 
animals. Then it is covered by a leathery green skin that 
is quite water-tight and air-tight. It has no leaves 
through which it gives off water as does the oak tree. 
There is almost no evaporation from it. 
Inside this cactus there are sections which resemble 
the wooden slats of a barrel and which keep the plant in 
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