Soil-Makers 31 



advance guard of the vegetable host, and their appear- 

 ance signifies that the fate of the lava surface upon 

 which they have settled is sealed. Nature has marked 

 it for her own. She is going to break down the hard, 

 barren surface sooner or latter, and convert it into a 

 fertile, productive soil, fit for field or vineyard. 



The lava has resisted for some time. For years it 

 did not even cool, and it has scorched innumerable lichen 

 spores to death in their attempt to settle upon it. Even 

 when the surface had cooled there was for a long time 

 heat enough within to dry all the life out of them ; while 

 multitudes have found the glossy surface too glossy 

 even for their powers of clinging, and have been blown 

 away as fast as they came. There are some streams of 

 lava which are as glossy now as when they were first 

 poured forth three or four hundred years ago, and no 

 lichens have as yet managed to gain a footing there. 

 But they are not generally kept so long at bay. They 

 return to the charge again and again, helped by the 

 pioneers who have also been at work meantime, and 

 have gradually roughened the surface a little, or at 

 least have taken off some of the glossiness ; and at 

 last the spores manage to, settle and fix themselves 

 so firmly that neither wind nor rain can dislodge 

 them, and they begin to grow and spread at their 

 ease. 



Then, in spite of what was said in the previous 

 chapter, these vegetables, at all events, must live on air 

 and water ? 



Not at all ! Lichens are very substantial feeders 

 indeed, and consume more mineral matter in propor- 

 tion to their size than any other plants. 



But if it is locked up, and not available until the rock 



