EFFECTS OF COLD 95 



finally are pressed against the soil under many 

 feet of snow. In this position they are also 

 secure from the shearing action of moving 

 masses of ice and snow above them. When 

 the snow melts in the spring the elastic 

 branches return to the upright position, and 

 the early climber may see the old leaves plas- 

 tered over with earth, and small stones ad- 

 hering to the twigs and branches. The gar- 

 dener imitates the action of these pines w^hen 

 he bends rose bushes and small shrubs to the 

 ground and covers them with earth and straw. 

 A very interesting method of avoiding 

 death by cold is afforded by many aquatic 

 plants. Species which float on the surface of 

 water owe their buoyancy to small bubbles 

 of gas in or between the cells. On the ap- 

 proach of winter, the gas is given off, and the 

 plant sinks to the bottom, either in the form 

 of spores or the entire vegetative body of the 

 plant. 



In such forms as the w^ater lily, the leaves 

 and flowers die down and the main stem of 

 the plant, a bulky rhizome loaded with food, 

 is securely imbedded in the mud below^ the 

 freezing line. At the beginning of each season 

 new leaves and flower-stalks are sent to the 

 surface. 



Perhaps the most interesting adaptation is 

 that offered by such aquatic plants as the 



