THE FEELINGS OF PLANTS 105 



by their parents are not likely to suffer harm from 

 the sun's rays. The so-called Compass Plant 

 (Silphium} has leaves which twist laterally when 

 the sun shines upon them, and in this way avoid 

 the injurious effects of too strong an illumination. 

 Many plants under the influence of very strong 

 sunlight droop their foliage ; partly, of course, 

 because of the excessive transpiration of moisture ; 

 but we may take it that the change in position 

 is a useful protective measure. 



As to the causes which underlie these light- 

 seeking and light-avoiding movements, we cannot 

 find any all-sufficing explanations. Certain it is 

 that they only continue so long as the plant is 

 in a growing state. We know that light has a 

 retarding influence on growth, and it has been 

 suggested that plants lean towards the point of 

 illumination because the shady side of the stem 

 extends more rapidly than the part which is 

 stiongly lighted. This theory does not help us 

 to understand how it is that parts of the plant 

 avoid the light. One cannot but feel that in all 

 these phenomena there is something more than a 

 mere mechanical adjustment, and that most of 

 these responses must be the outcome of inherent 

 tendencies which exist in the plant. Whilst a 

 little observation destroys the illusion that the 



