250 



table is from Dr. Wolif 's Aschen Analysen, and shows the variation in the 

 fir tree : 



LOG WOOD. BILLET WOOD. BRANCHES. ESD OK BR. 



Wood 11 .11 .17 .68 



Bark 65 .59 .67 1.10 



Sap .17 .18 .32 .78 



The variation during different parts of the year is also given : 



TREES— CHERRY. BIRCH. PINE. CHESTNUT. 



April 2.00 



May . . 3.59 2.12 



June 2.43 



July .95 2.32 2.81 . . 



August 1.57 



September 84 1.28 1.68 .70 



October 11 .49 .70 .62 



The table represents the per cent, of N in wood dried at 100°C. 



The source of the mineral constituents of the trees must be the soil, while 

 the atmospheric carbon dioxide, water and ammonia, furnish the 

 organic compounds which enter into the growth of trees. The H used 

 by the tree comes from the water, the carbon from the carbon dioxide and 

 the nitrogen from ammonia. There appears at present to be but little certain 

 knowledge as to the power of trees to absorb combined N directly from 

 the air as distinguished from that obtained from the same source through 

 the agency of the soil. The organic materials used by trees are the re- 

 mains of animals and plants, but even these must assume the mineral 

 form before they can become food for trees. The other mineral constiu- 

 ents are absorbed from the soil by the roots, after being first made soluble 

 by the decomposition going on in the soil, which renders them capable of 

 being taken up by the sap and distributed to all parts of the tree. NH3 

 is of the first importance to the vegetable world, and for its retention in 

 the soil four alkaline bases are made responsible. It is, therefore, always 

 present in an available form. Usually enough ammonia and nitric acid 

 are present in the atmosphere for vegetation, and by cultivation and accum- 

 ulation may take place in the soil. The mineral constituents necessary to 

 the growth of the tree are potash, lime, magnesia, and iron, phosphoric 

 acid, sulphuric acid, with possibly the addition of soda. 



The analyses of Bibra, Zoeller, Arendt, Bretschneider and others upon 

 the per cent, of soda in trees and plants leads to the conclusion that in 



