14 



LIVING PLANTS 



Sensitiveness 

 to light 



different organs ; it sets up movement of the 

 organ in response to stimulation ; the direction 

 of movement will depend upon the specific 

 kind of sensibihty acquired by that organ ; 

 the direction of the movement will always 

 bear some definite relation to the vertical 

 without regard to the position of the plant. 

 But, what other senses have plants ? Next 

 to a proper position, most plants need a suit- 

 able exposure to hght. I shall not attempt 



to show the nu- 

 merous and inter- 

 esting ways in 

 which plants re- 

 spond to light. 

 Everyone knows 

 how plants light- 

 ed from one side, 

 as when placed 

 before a window, 

 bend toward the 

 light. This is a 

 true sensitiveness, 

 for it results in 

 bringing about 

 definite movement. 

 The stems place themselves parallel to the di- 

 rection of the incident rays — that is, point to- 

 ward the window, while the leaves place them- 

 selves at right angles to the direction of the 



Fig. 2. — Charlock seedlings grow- 

 ing in a glass of water before a win- 

 dow. The stems bend toward the 

 light and the roots away from it. 



