102 WONDERS OF PLANT LIFE 



matter in the vegetable to external stimuli, and 

 thus find further evidence of the intimate relations 

 between all living things. 



In the old days it was often suggested that 

 plants cannot feel, although on what grounds the 

 assertion was made it is not easy to see. Reduced 

 to its simplest possible form, the ability to feel 

 merely indicates the power of response to a 

 stimulus. The iris of the human eye is so delicately 

 adjusted that it can feel the influence of light, 

 closing in round the pupil when an increase in the 

 amount of illumination takes place, and contract- 

 ing when the light-rays are few in number. It 

 is easy to prove that a plant can feel the light. 

 Place a healthy specimen in front of a window 

 in such a position that the light can only reach 

 it from one direction. In a few days the growth 

 of the plant is entirely altered ; its upright 

 bearing goes, and it leans over so that the upper 

 surface of its foliage may be fully exposed to 

 the stimulating rays. The same point may be 

 very strikingly illustrated if a small collection of 

 seedlings is grown in a box with a single aper- 

 ture, when it is seen that all the young stems 

 turn towards the path of the light. Some little 

 plants are astonishingly sensitive even to very 

 feeble illumination. 



