CHAPTER III 



SOIL-MAKERS 



Standing before some bare expanse of hard rock, we 

 might well wonder, if we knew nothing of the subject, 

 how it should ever be converted into a surface fit for the 

 support of vegetation. There may be vineyards close by 

 showing that it has been done in other instances; but 

 what is to be the first step? 



If we were to look closely at the seemingly bare sur- 

 face, we might, and in most cases would, find that it was 

 not altogether bare and barren. We might need a micro- 

 scope to show us the truth, but if we understood what we 

 saw, we would discover that the rock had been sown. 



The pioneer laborers, far from finishing, have hardly 

 begun their work here, but seed has been scattered in this 

 unlikely place; and if we look at what has been done in 

 other similar places, we shall see that it has not been 

 wasted. 



Floating about in the air, invisible, but in countless 

 multitudes, are — what answer to the seeds of other 

 plants — the spores of those strange forms of vegetation 

 called lichens, which, except in towns, are to be seen 

 beautifying every old wall, roof, and tombstone. They 

 are so light that they cannot settle at all, except when the 

 air is still, and even then the least breath would disturb 

 them. 



But they are sticky, and this stickiness enables them to 

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