40 MANURES FOR FRUIT TREES 



constituents of the soil available for the use of 

 trees and plants generally. 



Water. — Water is the most abundant substance 

 found in plants. The average quantity is about 

 70 per cent. Very succulent plants contain as 

 much as 80 or 90 per cent, of water, whereas in 

 the wood of fruit and other trees it is as low as 42 

 per cent. Trees require a large amount of water 

 for their growth, and it is necessary that the 

 supply should be abundant at all times, on account 

 of the loss through transpiration from the leaves 

 and the necessity of replacing the loss. If the 

 transpiration from the leaves greatly exceeds the 

 amount of water taken in through the roots, the 

 leaves shrivel and the tree suffers. 



It follows from the above-mentioned facts that 

 one of the most important functions of the soil is 

 the maintenance of a proper supply of water ; and 

 a soil should possess a certain retentive power for 

 water. This retentive power varies greatly in 

 different soils. Sandy soils maintain compara- 

 tively little moisture — due to their open texture. 

 They frequently contain only 5 or 10 per cent, 

 of moisture. Clay soils have very minute inter- 

 stices for water to pass through ; they offer a great 

 resistance to the percolation of rain. These soils 

 maintain from 15 to 20 per cent, of water. 



