fHE COMING OF LIFE g 



have yet suspected, for these ancient experimenters were great 

 utilizers of what at our first glance seems to us as mere by- 

 products, as they probably once were. Their present use and 

 value in the life of the organism is still but slightly understood. 

 One of these substances is chlorophyl, the green matter in 

 the leaves of plants by means of which they utilize the energy 

 of the light in the sun's rays to break up carbon dioxide and 

 build up starch. This is only one step in the process by 

 which the plant stores up food and potential energy and passes 

 it over to the animal. 



Chlorophyl is one of the most conspicuous characteristics 

 of plant life, but probably not the most fundamental. We 

 have noticed that the bacteria are surrounded by a cell-wall or 

 membrane. They cannot, like the amoeba, engulf solid par- 

 ticles, but live on fluid materials absorbed from the surround- 

 ing water. They do not need to go in search of their nourish- 

 ment, nor to recognize it when absorbed. They can remain 

 stationary, or float. 



In higher plants living on the land the water and dissolved 

 substances are gained by a subterranean root-system. The 

 chlorophyl is in the leaves exposing a very large amount of 

 surface to the light and air. Root and leaf surfaces are con- 

 nected by a stout elastic wooden trunk through which cur- 

 rents of sap flow upward and downward. The plant wastes 

 no energy in locomotion, its expenses are very small, its 

 income is steady and large; it has a large surplus balance to 

 expend in growth and reproduction. A highly successful 

 plant, like one of our weeds, can grow rapidly in comparatively 

 dry and poor soil, seeds abundantly, tolerates changes of 

 climatic and other conditions, and flourishes where our more 

 delicate plants would die. 



The cell-wall of cellulose, the fluid nourishment, the pres- 

 ence of chlorophyl are the chief characteristics of plants; yet 

 no one of these is peculiar to them; the ability to use CO. and 

 salts as building material for starch and protein is certainly 

 peculiar to them, however; every one can be found in some 

 animals. But in plants they are all combined in one highly 



