314 FOSSIL FLORA 



The complicated phsenomena of our district evidence frequent 

 oscillations of level, and repeated changes of land, freshwater, and 

 marine conditions. During the Carboniferous era, this district had 

 its hills and valleys, its rivers and lakes ; but there were also extensive, 

 low-lying plains, rank with vegetation, bordering on the sea. These 

 swamps were converted into lakes, and the submerged vegetation was 

 covered with sand and mud, in which were stems and branches of 

 trees ; other changes succeeded — the waters gradually became 

 shallower, and at length a new marshy surface appeared, supporting 

 a vegetation as luxuriant as before ; after the lapse of ages, the 

 scene is again changed — the vegetable accumulations have sunk — the 

 waters of the ocean have rolled over it, and eventually it is covered 

 with lime and mud beds which are crowded with marine animals, 

 that had lived and died on the spot where they are now entombed. 



The Carboniferous deposits have a wide range in both hemispheres, 

 from the arctic regions down to the 33° of north latitude. Over the 

 whole, the same general conditions prevailed, for the same peculiar 

 Flora is found in every portion of it. That Flora was not varied, 

 though extraordinarily luxuriant and enormous in the aggregate. At 

 present there are in Great Britain 1428 species of flowering plants 

 and Ferns, bvit only 300 species have been found belonging to the 

 Carboniferous era. The different proportion of Ferns is also remark- 

 able ; for while nearly one half of the Carboniferous Flora are Ferns, 

 they constitute only about g^th part of the entire existing Flora. 

 Conditions such as are indicated by the Carboniferous Flora are to 

 be met Avith only in countries, especially in islands, bordering on the 

 tropics ; and it may therefore be inferred that the climate of the era 

 was humid and equable, and, if not warm, at least temperate. This 

 conclusion is strengthened by some peculiar characters of the Coni- 

 ferous fossils found in the valley of the Tweed, for they have few 

 and very slight appearances of concentric rings, which arise from 

 interruptions of growth consequent on changes of temperature. 



The scenery of these primaeval lands, though not glowing with 

 beauty nor radiant with light, has its charms, and arrests attention 

 by the strangeness and vast proportions of its vegetation. The sum- 

 mits of the hills and slopes of the mountains were adorned by the 

 picturesque forms of the lofty Araucarias and other cone-bearing 

 trees ; on the extended swampy plains, dense forests of gigantic 

 Club-mosses flourished, their huge arms flung wildly out, and covered 

 with scaly leaves and terminated with cones ; fluted trees stood erect 

 on widely spreading roots, their long narrow leaves forming a series 

 of drooping curves rising from the summit and sides of the stem, 

 and giving to the scene sepulchral solemnity ; tall reeds sprung up- 

 ward, straight as the mast of a vessel, with slender leaves or branches 

 in whorls around the stem. The foliage of the whole was sombre, 

 but somewhat relieved by the brighter green herbaceous Ferns which 

 grew in the shade, and by the graceful Tree Ferns crowned with over- 

 arching fronds. No warm-blooded creature then " walked the earth " 

 — no beast roamed through the forest — no bird was there with its gay 

 plumage and sportive song ; only a few reptiles crawled in the swamps, 



