86 VEGETABLES. 



146. So fai as the four organic elements are con- 

 cerned, the plant obtains them from the air mainly, 

 either directly by the leaves, or through the surface 

 soil by the roots. 



14T. It would not be far from the truth to say that 

 the plant feeds itself about equally from the earth and 

 the air during its growth. Its inorganic matter, that 

 which remains as ash, when the plant is burnt, is ob- 

 tained wholly, from the ground, but is only a small 

 part of the whole, not more than from one to ten per 

 cent. It is probable that a poor, stinted crop is de- 

 rived from the soil and air in about the same propor- 

 tions as a luxuriant one. But the whole of such a crop 

 is a small affair. A part of it is still smaller ; and I 

 wish here to repeat and impress the thought, that the 

 better we do by our plants, in their ground relations, 

 the more they draw for as from the common stock of 

 vegetable food, which floats unseen in the air. 



FLOWERING AND SEED-BEARING OF PLANTS. 



148. One thing should be noticed with regard to 

 the flowering of plants. The flower-leaves, unlike 

 those of the other parts of the plant, absorb oxygen 

 by day as well as by night. The object of this ar- 

 rangement probably is to give them their beautiful 

 colors. The oxidizing of various substances changes 

 their hue. For instance, if a flower-leaf have in it 

 a trace of the protoxide of iron, the inhaling of oxy- 

 gen will give it a brilliant red. Other substances are 

 turned by the same cause into blue, yellow, violet, &c. 



