THE INA'EK LIFE OF PLANTS. 



321 



When a plant, such as the Mimosa (Fig. 30), or sensitive plant, 

 whose leaves droop when they are touched, is placed for some time 

 in darkness, the movements disappear completely ; and when such 

 a plant is placed in the light, the power of movement is not restored 

 for some hours, or it may be days. A sensitive plant, which is very 

 liable to be affected by alternations of light and darkness, may be 

 rendered motionless by being simply placed in a feeble light. In 



FIG. 31. OXALIS, OR WOOD SORREL, WITH CLOSED LEAVES 



such a case, or when placed in the dark, the plant becomes rigid. 

 In the Wood Sorrel, or Oxalis (Fig. 3 1 ), the leaves of which open and 

 close under stimulation, light causes the leaves to expand. In the 

 still more curious Desmodium gyrans (Fig. 32), or Moving Plant of 

 India, whose small lateral leaflets exhibit continual movements, both 

 vertically and in a circular direction, the motion continues even in the 

 dark, provided a proper temperature be maintained. This plant> 



