36 



or an apple are principally water taken from the soil by the roots. 

 Bat there is more than water, for the juice of an apple is sweet or 

 sour, wliile the sap and juice of other plants may be sweet or bitter. 

 There are some substances dissolved in the water. 



It is these dissolved substances that the plants need for their 

 growth, and they find them ready for use in the soil. There is a 

 plant-food which the roots seek and find, so that every plant which 

 sends roots into the soil takes something from it to build in the 

 plant tissue. The sharp edges of some sedges, which will cut the 

 hand like a dull knife, and the wood ashes left when a wood fire is 

 burned, represent in part this plant-food obtained from the soil. 



14. — A honldei^- strewn soil of glacial origin iHth one of the large erratics on the left 

 similar to those which early attracted atttotioa to the diift. See page 42. 



Let us take a handful of soil from the field, the school yard, or 

 the street and examine it. We find it to be dirt that " soils " the 

 hands; and when we try to brush otf the dirt we notice a gritty 

 feeling that is quite disagreeable. This is due to t-lie bits of mineral 

 in the soil ; and that these are hard, even harder than a pin, may 

 often be proved by rubbing soil against a piece of glass, which the 

 hard bits will scratch, while a pin will not. 



Study this soil with the eye and you may not see the tiny bits, 

 though in sandy soils one may easily notice that they are bits of 



428 



