22 



THE MODERN PEACH PRUNER. 



its functions as well as that of the leaves. The 

 sap ascending from the roots is developed therein, 

 the useless portions are evaporated into the atmo- 

 sphere, the nutritious substances remain in the cells, 

 where they are decomposed by the oxygen to form 

 nutriment for the growing fruit. These fruits 

 absorb a very large proportion of sap for their own 

 use, and do not restore it to the general use of 

 the tree as the leaves da. This is how the too 

 abundant production of fruit exhausts the vitality 

 of the tree, and how the crop of one year affects 

 that of the next. 



During the period of growth fruits inhale car- 

 bonic acid, and exhale oxygen ; but when quite 

 ripe they absorb oxygen, and set free carbonic 

 acid. When, then, all this acid is disposed of, and 

 replaced by oxygen, the fruit is perfectly ripe, and 

 decay is not far off. In all these processes we see 

 what an important part water plays, whether in 

 the soil as the means of conveying the nutriment 

 to the plant, or in the air in the condition of 

 vapour. In the soil it dissolves the substances it 

 meets there ; in the body of the tree, as sap, it is the 

 vehicle of these nutritive substances; and in the air, 

 in the state of vapour, it remedies any undue dry- 

 ness of the soil. A superabundance of humidity is, 

 however, an evil. Trees grow, but produce but 

 little fruit when moisture is too abundant. 



