OF THE PBECEl)l>G CHAPTERS. 177 



CHAPTER m. 

 Sottrces of the food of flants» 



Their organic food comes chiefly from the air. 



Carbonic acid, a gas, hea^ -s combus- 



tion, fatal to life; no color, s;. le, and pe- 



culiar smell. Furnishes carbon to plants. 



This gas is absorbed from the atmosphere by day, 

 through the leaves, and oxygen is at the same time 

 given offj iiVfth of carbonic acid exists in th« 

 air. 



How the supply of it is kept up; combustion, re- 

 spiration, decomposition. 



The hydrogti: ' from water. 



The oxjgen < :>onic acid, and 



almost every form of food. 



Nitrogen is supplied by ammonia and nitric acid. 



Ammonia, a gas, gives the smell to aqua ammonia, 

 and to " salts. 



Nitr ommon aqua fortis. 



CHAPTER IV. 



Of the organic nAAtnee of plants ; dmdure of the 

 dem, the rootsy and the branches. 



Principal bodies which make up the organic part 

 of plants. 



Woody fibre the most abundant of all, in rtema, 

 •talks, leaves, etc 



Starch, the leading ■nbstaiice in seeds, and in many 

 tubers. 



&igar. Gum. Oils. Their nattue and import- 

 ance. 



Thcae all composed of carbon, h y drogen, and oxygca 

 only, the two latter being in the proportUiM to ' 



