ABOUT FRUITS, FLOWERS AND FARMING. 137 



PRACTICAL USE OF LEAVES. 



There are two facts in the functions of the leaf, which 

 are worth consideration on account of their practical bear- 

 ings. The food of plants is, for the most part, taken in 

 solution, through its roots. Various minerals — silex, lime 

 alumen, magnesia, potassa — are passed into the tree in a 

 dissolved state. The sap passes to the leaf, the supei-fluous 

 water is given off, but not the substances tchich it held in 

 solution. These, in part, are distributed through the plant, 

 and, in part, remain as a deposit in the cells of the leaf. 

 Gradually the leaf chokes up, its functions are impeded, 

 and finally entirely stopped. When the leaf drops, it con- 

 tains a large per cent, of mineral matter. An autumnal or 

 old leaf yields, upon analysis, a very much larger propor- 

 tion of earthy matter than a vernal leaf, which, being yet 

 young, has not received within its cells any considerable 

 deposit. It will be found also, that the leaves contain a 

 very much higher joer cent, of mineral matter, than the wood 

 of the trunk. The dried leaves of the elm contain more 

 than eleven per cent, of ashes (earthy matter), while the 

 wood contains less than two/>er cent. ; those of the willow, 

 more than eight fer cent.., while the wood has only 0.45 ; 

 those of beech 6.69, the wood only 0.36 ; those of the (Eu- 

 ropean) oak 4.05, the wood only 0.21 ; those of the pitch- 

 pine 3.15, the wood only 0.25 per cent.* 



It is very plain, from these facts, that, in forests, the min- 

 eral ingredients of the soil perform a sort of circulation; 

 entering the root, they are deposited in the leaf; then, with 

 it, fall to the earth, and by its decay, they are restored to 

 the soil, again to travel their circuit. Forest soils, there- 

 fore, instead of being impoverished by the growth of trees, 

 receive back annually the greatest proportion of those 



* See Dr. Grey's Botanic Text Book, an admirable work, which every 

 horticulturist should own and study. 



