43 



MINERALS. 



1. Origin of soils. 



(a) Materials disintegrated rock and decayed organic matter. 



(b) Agencies at work water, air, frosts and glaciers, low orders 

 " of plants, earth worms, high orders of plants, chemical ac- 

 tion. 



\Vhat agents have you observed that are active during the winter? 



NOTE. The too common opinion is that plants should be studied only in 

 spring, summer, and autumn. The winter condition is the most trying, and 

 should have its attention. The individuality of the trees and shrubs is more 

 apparent, the characteristic branching, color and texture of bark, arrangement 

 and protection of buds. Observe the "winter rosettes" in the grass. 



There is such a ruthless destruction of the young evergreen forests 

 for Christmas that an effort should be made to have trees planted in 

 their places. 



In no place in the realm of nature is the using over and over again 

 of the same material more apparent than in the relation of plant life to 

 soil. The plants absorb the mineral matter through the roots and 

 the carbon dioxide through the leaves. When the different parts of 

 the plants have performed their functions they fall to decay the 

 carbon uniting with the oxygen of the air and passing into the atmos- 

 phere as a gas and the mineral matter reverting to the soil; the 

 plants form a connecting link between the mineral and animal worlds 

 and both finally return to the mineral world. 



To show that plants act chemically upon rocks, germinate a few 

 seeds in a clam shell or on a piece of marble; remove the soil and 

 observe tracing on shell or marble. Fold a piece of blue litmus 

 paper around the roots of beans and corn germinated between blotting 

 paper. The color will turn to pink showing the acid reaction, prov- 

 ing that the roots are giving out an acid. Dissolve a piece of egg 

 shell, coral, clam shell, marble and limestone in strong vinegar or 

 hydrochloric acid. Try clay sandstone and granite; which yields to 

 the acid? What kind of rock would plants affect most? Have you 

 observed any instances when the growth of roots has split the rocks? 

 The roots of plants make the soil more porous and allow water con- 

 taining acids in solution to have access to underlying rocks, causing 

 them to disintegrate. Note the variety of mosses and lichens on 

 granite boulders and exposed surfaces of rock. What is their ef- 

 fect? What relation do you see between the water, air and frost 

 and disintegration of rock? 



