48 The Living Plant 



the establishment to the exigencies of a fixed income. This is 

 the real meaning of the photosynthetic adaptations, which it is 

 now our business to consider. Each one of the physiological 

 processes of plants produces, of course, in like manner its 

 effect upon their structure; but the one process of photosynthesis 

 far surpasses all others, indeed all others put together, in 

 the profundity of its influence in making plants what they 

 actually are. The evidence thereof will appear in the following 

 pages. 



The photosynthetic essentials for which plants are dependent 

 upon the environment are in reality four, because, in addition to 

 light, carbon dioxide, and water, plants need also, for reasons that 

 will later appear, certain minerals, which are, however, for the 

 most part very widely distributed in soils. Now in showing the 

 way in which these four are supplied by the environment to plants, 

 I must recall to the reader some very familiar and commonplace 

 facts. But I remind him that there is nothing in the world so 

 difficult to see in its real significance as the commonplace; more- 

 over let him remember the truth expressed by a brilliant writer 

 in the saying that little minds are interested in the extraordinary, 

 but great minds in the commonplace. 



The crucial facts about the mode of supply of the four photo- 

 synthetic essentials are these. 



First. They all exist widely even if not abundantly distributed in 

 nature, and moreover are incessantly in movement or circulation, 

 the light with the swing of the sun through the heavens, the car- 

 bon dioxide with every breeze that stirs the still air, the water 

 in the form of the mists and the rain, and the minerals in solution 

 in the water which soaks and drains through the soil. Therefore 

 plants have no need to go in search of these essentials, as animals 

 must for their food, but are able to stay fixed in one place and 

 allow the essentials to be brought them by the general circula- 

 tion of nature. This method renders needless any self-motive 

 power, with the accompanying muscular system and jointed skele- 



