STUDIES IN NATURE 



ing than if they were left lying out on the surface 

 of the ground, and helps to provide for a suc- 

 cession of young trees. The bark of the oak 

 tree until quite recently was also an extremely 

 valuable crop, for it was used in the preparation 

 of skins or tanning of leather. Now, however, 

 our men-of-war are built of steel, our pigs are 

 not so often driven out into the woods, and the 

 tanning of skins can be done without the use of 

 oak-bark. In spite of this the value of oak- 

 wood has steadily increased, and the supply of 

 food wood in England is not equal to the 

 emand. 



The gradual decay and fall of the leaves 

 marks, as we know, the autumn season, and 

 then in towns and gardens we see men busy in 

 sweeping up the leaves and carrying them 

 away. This may be necessary in parks and 

 exposed gardens where the wind might scatter 

 the leaves about, but in big sheltered woods 

 the leaves lie under the trees, helping to keep 

 the roots warm and moist in winter-time, and 

 when in the course of time they decay, they 

 give back to the soil the substances the tree 

 took from it to make them. In Nature there 

 is no waste ; the tree gives back to the air some 

 of the moisture that fell as rain, and the leaves 

 return to the soil out of which they were made. 



(118) 



