90 WHY rLANTij GUOW, 



plants have been making, day by clay, since God said, Let the earth bring forth 

 grass, and the herb yielding seed, and the fruit-tree yielding fruit after his kind^ 

 whose seed is in itself, upon the earth, — and it was so ? The answer to these ques- 

 tions will show us plainly 



279. What Plants are made for. In the first place, in the very act of making 

 vegetable matter, plants fulfil one great purpose of tiieir existence, that is, 



280. They purify the air for animals. That part of the air which renders it fit 

 for breathing is called oxygen ; this makes up about one fifth part of the air we 

 breathe. At every breath animals take in some of this oxygen and change it 

 into carbonic acid ; that is, they combine the oxygen with carbon from tlieir blood, 

 which makes carbonic acid, and breathe out this carbonic acid into the air, in place 

 of the oxygen they drew in. Now this carbonic acid is unfit for the breathing of 

 animals, — so much so, that, if it were to increase so as to make any considerable i)art 

 of the atmosphere, man and other animals could not live in it. But plants prevent 

 the carbonic acid from accumulating in the air. While animals need the oxygen of 

 the air, and in using it change it into carbonic acid, hurtful to them, plants need the 

 carbon of this carbonic acid ; indeed, it makes a very large portion of their food, — 

 as we plainly see it must, when we know that about half of every part of a plant is 

 carbon, that is, charcoal. And this carbonic acid is the very jiart of the air that 

 plants use ; they constantly take it from the air, decompose it in their leaves during 

 sunshine, keep the carbon, and give back the oxygen pure, so keeping the air fit 

 for the breathing of animals. The carbon which plants take from the air in this 

 way, along with Avater, &c., they assimilate, that is, change into vegetable matter : 

 and in doing this 



281. They make all the food ivhich animals live vpon. Animals cannot live upon 

 air, water, or earth, nor are they able to change these into food Avhich they may 

 live ujion. This work is done for them by plants. Vegetable matter in almost 

 every form — especially as herbage, or more concentrated in the accumulations of 

 nourishment Avhich plants store up in roots, in bulbs and tubers, in many stalks, 

 in fruits, and in seeds — is food for animals. ^'- And to every beast of the earth, and 

 to every foivl of the air, and to everything that creepeth vpon the earth,'' as well as 

 to men, is given " every green hei'b for meat." Some animals take it by feeding 

 directly upon vegetables ; others, in feeding upon the flesh of herbivorous animals, 

 receive what they have taken from plants. Man and a few other animals take in 

 both ways what plants have prepared for them. But however received, and how- 



