8 SOILS 



send their minute root structures into the crevices 

 and live upon the slight substances that are formed 

 on the surface by weathering, together with what 

 they can get from the air. These lichens are very 

 acia and are able to etch the rocks. They die and 

 decay, leaving the beginning of a fertile soil in the 

 crevices and upon the ledges. The growth of 

 higher plants is thus made possible; perhaps the 

 mosses gain a foothold. These in turn elaborate 

 more of the rock for their own use and in turn die, 

 enriching the soil with themselves. Now there is 

 a pocket of soil upon the ledge which may be able 

 to support such humble plants as ferns or saxifrage. 

 Thus the process goes on from decade to decade 

 and from century to century, the lower plants being 

 succeeded by larger and more highly organised 

 plants, as the rocks are made finer by weathering 

 and are enriched by the decay of the plants that they 

 nourish. Finally the soil can support mulleins, 

 honeysuckles, or fir trees. Many years later it 

 may be able to support a crop of corn, timothy, 

 or apples. A fertile farm soil is the product 

 of many agencies working through thousands of 

 years. 



How Plants are Making Soil To-day. Plants are 

 helping to make fertile soil to-day as they have for 

 centuries. Each year the forest floor receives a 

 fresh carpet of leaves, and the older generations of 

 trees fall to the ground and slowly pass into mold. 

 Each year the grass in the meadows and the weeds 

 by the roadside add their substance to the soil from 

 which they have sprung, thereby enabling it to 

 nurture other and lustier plants in succeeding 

 years. Lichens spread their thin substance over 

 rocks, and mosses take up the battle where the 

 lichens leave off, just as of old. 



