242 



therefore always be proportional to the quantity of mineral constituents 

 of nutrition present in the soil in a soluble or available form. This would 

 of course always be more or less influenced by accidental conditions in 

 the surroundings. With the organic constituents of trees we are not to 

 deal, but much has already been done on this subject. 



THE WATER IN TREES. 



The average amount of moisture in some of the more common trees may 

 be seen from the fallowing : 



Ash 28.7 per cent., beech 29, birch 31, elm 44.5, pine 50, oak 40, maple 

 34, hemlock 45, pear (Howell) 53.7, apricot (Russian) 44.4, cherry (Wins- 

 low) 51.8, cherry (May Drake) 50.1, poplar 51.1. 



The samples of fruit trees were all taken on the same day, cut fine, dried 

 at 110° C. until constant weights were obtained. The per cent, of mois- 

 ture is much lower in trees than in grasses, cereals or tubers. 



There is a considerable variation in the per cent, of moisture in difi"er- 

 ent parts of the same tree as is shown by the following determination 

 given by Stockhardt. Fir tree cut May 20 : 



Tree trunk with bark, 36.15 per cent. ; thin end of trunk, 50.8; branches 

 over 1 c. m., 47.95; branches under 1 c. m., 51.56; leaves, 52.49. 



According to Galesnofi" the per cent, of water after increasing from be- 

 low upwards diminishes again at the summit of the trunk. Not only 

 does the average per cent, of water vary in different parts of a tree but 

 also in the same part there is a variation during different seasons of the 

 year, as shown by the following table also from Stockhardt : 



BEACH TREE. 

 LOWER, xMIDDI.H. UPPER. 



Winter 50.5 41.5 39.3 



Spring 43.7 42.8 47. 



Summer 42.1 44.1 48. 



Autumn 39. 40.1 40.1 



In ordinary dry wood there is about 15 per cent, of water. 



THE ASH OF TREES. 



Experiments show that while different trees and different parts of the 

 same tree vary much in their proportion of ash, yet in the same parts of a 

 given species of trees, the quantity of ash remains about the same and its 

 chemical composition though widely varying in different trees is similar 

 for the same parts of the same species, although the soils on which they are 

 grown may differ much in character. Each individual tree seems to make 



