420 JOURNAL OF FORESTRY 



Certain plant cells produce oxalic acid ; when calcium salts are 

 present, if they are distributed throughout the tissues of ligneous 

 plants, this acid forms oxalate of calcium. It is found in the bark, and 

 especially in the inner bark. Its development with the advancing season 

 is the same as that of starch, increasing from May to October; but it 

 is already present in fairly large quantities when starch has hardly 

 begun to form. 



One of the most important and abundant of the glucosides in lig- 

 neous plants is tannin. It is an important product of the bark of oak 

 coppice. It is found in solution in the cellular fluid, or in the form 

 of minute intra-cellular masses, as in the bark of oak, poplar and 

 birch. Tannin in fruits may be considered as a reserve product, since 

 it is transformed into glucose, while in the barks and young wood of 

 ligneous plants it is a product of elimination. Its maximum quantity 

 is reached in summer ; it forms about one-fourth the weight of gall 

 nuts, spherical excrescences resulting from the boring of synips in 

 the oak. It has been proved that young oaks with smooth bark, that 

 is, in the best state of growth, furnish the largest quantity of tannin. 



Wood ash varies with the soil and with conditions of growth. The 

 proportion in weight of soluble salts (chiefly potassium salts) contained 

 in the ash is about 18 per cent. The following bases are found in the 

 ash: lime, 56.73 per cent; potash and soda, 16.81 per cent; other 

 oxides, 2.08 per cent; and acids: phosphoric, 9.44 per cent; sulphuric, 

 2.50 per cent. 



Lime and silica are found principally in the bark ; potassium in the 

 leaves and wood. The parts of the tree containing the largest per- 

 centage of ash are, first, the leaves and the root hairs, then the bark, 

 the branches, the trunk, and lastly the roots. 



Chemical analysis of the tree gives carbon, hydrogen and oxygen 

 gases; nitrogen, sulphur, phosphorus, chlorine, silicium, potash, calcium, 

 magnesium, iron, sodium, and sometimes aluminum ash. 



Many other substances have been discovered in plant tissue, the 

 properties of which cannot be determined by chemical analysis. 



