450 SELECTIONS FROIM ADDRESSES. 



sheaths the sap vessels, and covers the exterior of the hollow 

 stems of the cereal ia or grasses. 



Chlorine is found combined with the metalic bases of soda 

 and potash, forming, with sodium, the well known sea salt, 

 chloride of sodium ; and with the basis of potash, chloride of 

 potassium, and with those of lime and magnesia, the very sol- 

 uble chlorides of calcium and magnesium. These salts, ab- 

 sorbed from the soil, also undergo decomposition, and produce 

 other combinations in the plant. 



Fluorine, not yet detected in the ashes of plants, must 

 exist in them in small proportions, for it generally accompa- 

 nies phosphate of lime, and it forms a constituent of the en- 

 amel of teeth, and occurs in small proportions in the bones of 

 all animals. 



The minerals constituting the substantial basis of all soils, 

 must contain all the fixed elements found in plants grown upon 

 them ; but it often happens that they contain too small propor- 

 tions of the most important elements, to furnish, for a length 

 of time, the inorganic constituents of crops that are removed 

 from the soil. 



The native forest, every year, pays its tribute of deciduous 

 foliage, and thus, in part, renovates the soil ; but still more by 

 the ultimate decay of the aged trunks of trees, is the soil 

 replenished with the materials drawn from it by them during 

 their growth, and, for interest, is added those materials which 

 the trees had withdrawn from the atmosphere. The organic 

 matter thus derived, acts on the mineral ingredients of the soil, 

 various acids being produced, which dissolve the tardily decay- 



ling minerals in the soil. 



Thus, forest trees do not rob the soil of any of its constitu- 



.ents, and it remains ever able to renew their growth. 



Fire, though it dissipates the organic matters, leaves all the 



i fixed saline matters of wood in its ashes, and by the sudden 



.addition of so much readily soluble mineral matter, alters the 

 character of the soil, so as to enable it to bear plants and trees 



ithat did r]( t grow upon it before. 



Thus we see an abundant growth of raspberry bushes and 



■of cak trees where a pine forest had been destroyed by fire : 



