CHAPTER IX 



THE FOOD OF PLANTS, AND HOW THEY SECURE IT 



" Self-preservation is the first law of life." So runs 

 a truism hoary with antiquity. For lack of a better 

 way of putting it, the assertion is ventured that deep 

 down, and ineradicable in the living plant, is the im- 

 pulse to live — an impulse which involves not merely 

 self-preservation, but also the effort towards racial im- 

 mortality. Where there is life there is also growth, and, 

 moreover, reproduction. In reproduction the parent 

 plant may seemingly perish, and " leave not a wrack 

 behind," but, in truth, its potency is transmitted to 

 posterity. As to its outer garb, it returns to Mother 

 Earth ; but as to its inward mystery, it lives still in its 

 progeny. 



In order that plants may live, and consequently grow 

 and propagate their kind, they must be suitably nour- 

 ished, and, in addition, defended against influences 

 inimical and fatal to the welfare of their vital proto- 

 plasm. The defences of plants will receive considera- 

 tion later. Our subject for the present is the food of 

 plants, how it is secured and utilized. 



The vital unit of plants is the protoplast, the little 

 protoplasmic body which is truly the " cell," and in- 

 cludes all the living constituents — nucleus, chloroplasts, 

 etc.— of the cell. A one-cell plant, such as a Desmid 



250 



