OTHER USEFUL PLANTS 87 



The barbarian could tear down the temple, 

 but he could not rebuild it. 



Similarly the chemist can tear the carbon- 

 hydrate molecule to pieces, but he cannot put 

 it together again. He knows how to pull to 

 pieces the molecule of sugar, for example, mak- 

 ing it into a simpler form of sugar, but 

 he cannot build up even the simplest form of 

 sugar from elementary atoms, were these ever 

 so freely supplied him. 



Carbonic acid is everywhere in the air, and 

 water may be had for the asking. 



The chemist knows just how many molecules 

 of water he should take to combine with just so 

 many atoms of the carbon to make a molecule 

 of sugar or a molecule of lupulin. 



But he does not know how to go about the task. 



His only resort is to appeal to the agricul- 

 turist in the field, who deals with living labora- 

 tories in which the method of compounding 

 these intricate substances is understood. 



If the chemist would have sugar, he must seek 

 it in the product of the cane or sorghum, or 

 beet. If he would have lupulin, he must go to 

 the hop vine, for this plant alone has learned the 

 secret of its production. 



So it chances that the ancient calling of the 

 agriculturist is as essential to-day as it has al- 



