28 HORTICULTURE LECT. n 



Soils made from the crumbling of rocks alone and 

 composed chiefly of silica (sandy), alumina (clayey), 

 magnesia, potash, soda and iron all minerals- 

 are "inorganic," because they are not composed of 

 something that once lived, or of the remains of plants 

 and animals. Soils that are composed of such re- 

 mains of something that once had organs of life, 

 something in fact that once grew, then died and 

 crumbled to mould as do fallen leaves, decaying 

 vegetation and animal refuse, are li organic." 



It is well to know these things, and the benefits 

 derived by mixing soils and adding manures will be 

 the more readily comprehended. 



Soils composed of mineral matter chiefly inorganic 

 contain elements that give firmness and substance 

 to growth ; for instance, without silica the stems of 

 wheat and other grain crops would be soft and fall 

 over, as is the case in black peaty and bog soils in 

 fens, which are mainly of vegetable origin. With- 

 out potash and lime, derived from rocks, we could 

 not have full crops of the best potatoes ; without 

 phosphoric acid and potash we could not have superior 

 cabbages or turnips ; while carrots could not be 

 perfect without soda, nor parsnips without lime ; and 

 as will be subsequently explained, it is by pro- 

 viding the mineral and non-mineral essentials for 

 crops in the right proportions that the best results 

 are obtained. 



We now turn to vegetable soil. It is this that 

 gives richness to the earth and force to growth. 

 When soil is new first formed by crushed and 

 powdered rock, it is necessarily bare, but does not 

 long remain so. The seeds of weeds and spores of 

 mosses settle on it, and with requisite moisture soon 

 germinate and cover the surface with plants which 

 grow and die, leaving behind them a film of dark 



