HOW PLANTS EAT. 37 



plants themselves, are entirely built up of living 

 jelly which this green-stuff has manufactured 

 under the influence of sunlight. And the mate- 

 rial that does this is such an important thing in 

 the history of life that I will venture to trouble 

 you with its scientific name, CHLOROPHYLL. 

 When sunlight falls upon the Chlorophyll or 

 green-stuff in a living leaf, in the presence of 

 carbonic acid and water, the chlorophyll (or, to be 

 quite accurate, the living matter or protoplasm 

 with chlorophyll embedded in it) at once proceeds 

 to set free the oxygen (which it turns loose upon 

 the air again), and to build up the carbon and hy- 

 drogen (with a little oxygen) by various stages 

 into a material called starch. This starch, as you 

 know, possesses energy that is to say, latent light 

 and dormant heat and movement, because we can 

 eat it and burn it within our bodies. Other mate- 

 * ials, hydro-carbons and carbo-hydrates, as they 

 are called, are made in the same way. The main 

 use of leaves, then, is to eat carbon and drink 

 water, and, under the influence of sunlight, to take 

 in energy and build them up into living material. 

 The starch and sugar and other things thus 

 made are afterwards dissolved in the sap, and 

 used by the plant to manufacture new cells and 

 leaves, or to combine with other important mate- 

 rials of which I shall speak hereafter, in order to 

 form fresh protoplasm with chlorophyll in it. 



Now we know what leaves are for; and you 

 can easily see, therefore, that they are by far 

 the most essential and important part of the 

 entire plant. Most plants, in fact, consist of 

 little else than colonies of leaves, together with 

 the flowers which are their reproductive or- 

 gans. We have next to see What Shapes various 



