58 LIFE ON THE FARM. 



other parts also to play, and the leaf is the organ 

 in which the wonderful work goes on. Water 

 consists of hydrogen and oxygen strongly bound 

 together. The leaf has the power of breaking 

 them apart, and combining them with carbon to 

 form starch, sugar, fat, and other substances com- 

 posed of these three elements carbon, hydrogen 

 and oxygen. 1 The carbon is obtained from the 

 carbonic acid gas of the air. Carbonic acid gas is 

 composed of carbon and oxygen. Only a fraction 

 of one per cent, of the atmosphere consists of car- 

 bonic acid gas, yet there is always some floating 

 everywhere, and the leaves struggle hard to get 

 every molecule that passes. 



There is in every living leaf an active, green sub- 

 stance called chlorophyl. It has the power, under 

 the influence of sunlight, to break-up water and 

 carbonic acid gas and form them into starch. 

 The starch is changed into similar compounds with 

 a different proportion of the atoms of carbon, 

 hydrogen, and oxygen. The leaf, then, is the fac- 

 tory in which organic material is made; chlorophyl 

 is the machinery, and sunlight is the motive power 

 that does the work. Organic compounds or the 

 compounds of carbon can always be recognized 

 from the fact that, on being heated sufficiently, a 

 black, charred mass remains. The charred mass is 

 carbon taken from the atmosphere by the growing 



'The formula for starch is C e H 10 O 5 , and for sugar C 12 H 22 O 1 ,. 



