The Story-Book of the Fields 



more easily penetrated by air and water. 

 Also, by the slow combustion carried on within 

 it, it constantly gives out a small amount of 

 carbonic gas which is absorbed by the roots. 

 Cultivation can only prosper if the ground 

 contains a sufficient amount of humus. Wheat 

 requires a proportion of almost 80 per 

 cent., while rye and oats are satisfied with 

 20 per cent. In poor, sandy ground, occa- 

 sionally the whole crop is turned over and 

 buried so as to be altogether converted into 

 humus. A meadow or a field of clover is 

 sometimes treated in this way. When it is 

 proposed to improve land by this means the 

 plants that are first cultivated in order to be 

 buried afterwards must be such as derive the 

 greater part of their constituents from the 

 atmosphere as the ground is unable to sup- 

 port them. Among the plants which satisfy 

 this condition are buckwheat, clover, lupine, 

 beans, vetches, lucerne and sainfoin. 



Humiferous soils have for their principal 

 component the brown matter produced by 

 the decomposition of leaves and other vege- 

 table remains. The chief of these is turf. 

 Turf is a blackish, spongy substance, formed 

 in damp flat ground by an accumulation of 

 vegetable remains and especially of mosses. 



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