32 THE RUBBER TREE BOOK 



the outer shells of the yonng roots, and certain hair-like offshoots 

 springing from them (root-hairs), possess thin walls through 

 which water is sucked in. Root-hairs have a corroding action 

 upon the soil particles by virtue of an acid they excrete, and 

 the mineral food they dissolve, along with that already in 

 solution, passes into them with the soil-water and then into the 

 cells themselves. From these outer cells the water carrying 

 the mineral food passes from cell to cell on to conducting-tubes 

 in the interior of the roots, and thence up through the stem 

 till it reaches the leaves. 



The structure of the older parts of the root-system closely 

 resembles that described in the next chapter as being that of 

 the stem. 



A good root development is essential to the welfare of the 

 tree. While the foliage manufactures much of the food re- 

 quired for the growth and the renewal of the cells, the salts 

 necessary for the tree's existence and continued growth are only 

 derived from the soil. 



The green colouring-matter in the leaves of the tree, called 

 chlorophyll, for example, could not be formed if there was no 

 iron in the soil which could be dissolved and thereafter absorbed 

 by the roots, and in due course reach the leaves. Leaves might 

 grow 7 on the branches, but they would not be green leaves, and 

 if not green they could not, with the assistance of the sunlight, 

 convert the carbonic acid gas of the atmosphere into carbon 

 compounds to build up the structure of the tree, and there 

 would be no growth. The quantities required of some of the 

 mineral salts may be but small, yet they are thus absolutely 

 indispensable. 



The more meagre the spread of the roots, the more re- 

 stricted the feeding area of the roots. A widespread area 

 means greatly-multiplied stores of food-stuffs at the disposal 

 of the tree. In stiff clay soils the spread of the roots is much 

 restricted, unless the soil is loosened by cultivation. Where 

 trees are closely planted the roots of the trees have to contend 

 with each other for space and they become matted together. 

 Wide planting is as essential for the healthy development of 

 the roots, and therefore, ultimately, of the tree, as an abundance 

 of light and air is for the foliage. 



Roots must have sufficient supplies of air in the soil for 



