72 THE GARDEN OF EARTH 



All parts of the soil are not alike. Here may be found 

 more water; there, less water. Here are more of such 

 salts and other foods as are needed, dissolved in water ; 

 and there are smaller quantities. And the business of 

 the root is to find out where it can get just that kind 

 of food, and just that amount of water, which the 

 plant must have if it is to grow and be in good health. 



So, as the root gets longer and longer, its tips go 

 steadily circling onward, making their way towards 

 what is wanted. 



If a root-tip touches a part which has the wrong 

 sort of food, or not enough water, what do you suppose 

 it does ? It simply turns aside and tries elsewhere. 



And when it draws near to a part where there is 

 abundance what then? Why, it goes in that direc- 

 tion, and the tips on arriving at the place send out 

 tiny root-hairs to suck in food and water. 



Far away in the cold north the ground is always 

 hard-frozen a little way below the surface, not only 

 in the winter, but all the year round. Many shrubs 

 and fir-trees manage to flourish even under such 

 difficult conditions, helped by the sun. And the roots 

 of these plants start off just as do others farther south 

 to travel straight downwards. 



But before long they come near to the hard frozen 

 under-soil. What do you think they do then ? Would 

 you expect them to go steadily, doggedly, boring onward 

 into the ice ? 



Not they ! As soon as they get near to the frozen 

 soil, and before they reach it, they make a sharp bend, 

 and journey along keeping to the same level, going no 



