Read it through once

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--Cañons in America.