The Response of Plants 149 



to beam, from wall to wall. He could hear ; he heard the 

 dripping of waters near and far, he heard the melan- 

 choly murmur of the busy world far above his head, he 

 heard the echoes of his own footfall and the cries of 

 noisome bats that struggled with each other in the night. 

 At length he found a single point of light. Toward this 

 he urged his way, climbing a long abandoned shaft at 

 length emerging to the open day more dead than living. 

 Which more responsive to the beam the bewildered 

 miner, or the imprisoned plant? 



Darwin made some wonderful experiments in this field 

 of our inquiry. The shooting blades of a sprouting grass 

 bent toward a distant lamp which emitted so little light 

 that a pencil held vertically close to the plants cast no 

 shadow which the eye could perceive on a white card. 

 These delicate shoots were therefore affected by a differ- 

 ence in the amount of light on their two sides, a differ- 

 ence which the eye of the trained naturalist could not 

 perceive. " Light seems to act on the tissues of plants,'* 

 says Darwin, "almost in the same manner as it does on 

 the nervous system of animals." Probably, I dare to 

 add, in just the same way, but far more delicately, and 

 through wider spectral range. 



But this is not all. The fact is the plant, while thus 

 exquisitely responsive to the light, is yet after all not 

 subordinate to its power. Certain parts of plants habit- 

 ually turn from the light. Thus the tendrils of the 

 grape bend away, as surely as its leaves spread to the 

 sun. It is advantageous to the grape to seek support 

 by its tendrils, but why this support should be sought 

 in the background is less evident; perhaps that there be 



