CHAPTER XXII 



SOIL. 



When children understand something of the 

 nature, function, origin and general composition 

 of soil, their gardening will have an added in- 

 terest. The constituents of soil are mingled 

 fragments of various kinds of rock material, 

 organic matter of vegetable and animal remains, 

 and crystals deposited from oversaturated solu- 

 tion of soil-moisture. The surface soil consist- 

 ing of the top to the depth of six to twelve inches, 

 to which the garden is most closely related, is 

 composed of fine rock fragments, while the 

 deeper portions compose the subsoil. The evo- 

 lution of plants was coincident with the evolu- 

 tion of soil, and the evolution of plants made 

 possible the evolution of animals^ — the organic 

 remains of which have a close relation to the 

 fertility of the soil. The soil is the scene of the 

 greatest activity of life and energy. One of its 

 most important uses is to act as the storehouse 

 for water to be used by plants. The productive- 

 ness of soil is determined largely by the amount 

 of water it can hold, the manner in which it is 

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