CHAPTER II. 



CHEMISTRY AND PHYSICS OF PLANT LIFE. 



Nature of Plant Food and how it is obtained. Influence of Light 

 on Plant Life. Influence of the Vegetable Kingdom on surroundings. 

 Origin of Carnivorous Plants. Saprophytes. Parasites. Retro- 

 gression. 



/CHARACTERISTIC plants furnished with the green 

 ^.s colouring matter called chlorophyll, as previously 

 stated, feed on inorganic food obtained partly from the 

 atmosphere, partly from the soil or substance in which 

 the roots are fixed. The only food material obtained from 

 the atmosphere is carbonic- dioxide (C0 2 ) ; the remainder 

 is taken in by the roots dissolved in water, and although 

 different food substances are required by different plants, 

 yet the following may be considered as being indispen- 

 sable to the majority of plants : 



Carbon (C), Hydrogen (H), Oxygen (0), Nitrogen 

 (N), Sulphur (S) ; these form the organic compounds 

 of the plant, that is to say, combinations of carbon with 

 other elements which, on exposure of the plant to great 

 heat, are for the most part resolved into volatile pro- 

 ducts, as water (H 2 0), carbonic dioxide (C0 2 ), ammonia 

 (NH 3 ), etc. 



Phosphorus (p), Potassium (K), Iron (Fe), Calcium, 

 (Ca) , Magnesium (Mg) ; these go to form the inorganic 



