296 



LIVES OF PLANTS AND ANIMALS 



burst when brought to the surface where the pressure is so much 

 less. Few forms of life have adaptations which enable them to 

 get along with the shortage of oxygen at greater depths. 



The muskrats make their homes of sticks, mud, and grass in the banks or water of streams, 

 ponds, and lakes. They feed on fresh water clams and lily roots which they get from the bot- 

 tom of the stream. They usually swim under water, rising only now and then to get air. 



Plants growing in dry or desert conditions, as cactus, sagebrush, 

 and aloe, show a leaf surface invariably reduced, sometimes in the 

 form of spines, as in the cactus. The stem may be thickened to 

 store water and a covering of hairs or some other material may be 

 present to lessen the loss of moisture by evaporation. If the 

 water or saturated soil, in which the plant lives, contains salts, 

 such as sea salt or the alkali salts of some of our western lakes, 

 plants living there show many characteristics which those in desert 

 conditions show. 



Animals living under such conditions are usually few and | 

 restricted to those that can burrow to depths so that they may ; 

 escape the heat, or lizards and snakes which are able to escape the | 

 heat by taking shelter under rocks. All forms of animal life found 

 there are able to live on small quantities of water. The desert 



