CHAPTER XIII 

 ROCKS, STONES, AND SCENERY 



An old wall — Beautiful colours — Insects — Nature's chief aim— Hard 

 times of lichens— Age of lichens — Crusts— Mosses— Lava flows of 

 great eruptions— Colonizing plants— Krakatoa— Vesuvius — Greenland 

 volcanoes — Sumatra — Shale-heaps — Foreigners on railway lines — 

 Plants keep to their own grounds — Precipices and rocks — Plants 

 which change the scenery — Canons in America. 



AT first sight, and when one is striding along at some 

 ZJL four miles an hour, there seems to be nothing at all 

 interesting in an old wall. But if one stops and care- 

 fully examines the stones, there is a great deal that is 

 interesting. 



Rocks and walls possess a fascination of their own. 

 Probably at least 2000 British plants are only found upon 

 them, and yet of these, the vast majority are so small and in- 

 conspicuous that an ordinary person never perceives a single 

 one of them. 



It is perhaps on rocks or old walls near the sea that this 

 stone flora is most richly developed. The nearly circular 

 orange-yellow patches of the Lichen Physcia parietina are 

 quite distinct and conspicuous. But any old wall, provided 

 it is well out in the country, is pretty sure to be interesting. 



At first it seems to have only a dull grey or neutral tint. 

 But if one goes to four or five feet distance, one discovers 

 that many shades of brown, red, white, and black go to make 

 this grey. 



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