34 



Soil-Makers 



The pines are much more imposing in appearance, 

 and look capable of much greater exertion (as they are 

 in some ways), but they could not have done what the 

 lichen does ; and, but for the hchen, they could never 

 have grown here at all. 



We see, then, that nature makes large use of the 

 humbler vegetables in preparing the way for the crops 

 which are eventually to be grown ; but it must not be 

 forgotten that the process of preparation is an exceed- 

 ingly complicated one, performed, not by one set of 

 labourers, but by many, all working together. 



Even a very scanty covering of vegetation does 

 something, it is true, to protect the rock below against 

 the battering of the rain and against changes of 

 temperature ; but, on the other hand, it keeps the rock 

 damp, and moisture not only dissolves on its own 

 account, but attracts gases from the atmosphere, which 

 greatly increase its powers in this respect. Then, too, 

 the powerful gas, carbon dioxide, is also formed in the 

 soil itself by the decay of vegetable matter, besides 

 being given off by living roots, and this greatly enhancesr 

 the dissolving power of water. 



Lichens, as we have said, are able to eat into the 

 rock, as oxygen eats into iron, and by similar means, 

 for both are strongly acid ; and on removing lichens 

 from a stone one sees indentations, similar to those 

 left on a piece of iron by the removal of rust. But 

 what is true of lichens is true in a degree of all 

 plants. The roots of all plants, that is to say, are 

 acid, though in a less degree, especially the young, 

 fine, hair-like roots; and if these find their way 

 through the thin soil to the rock beneath, they eat 

 into it, leaving a distinct impression of themselves 



