STATE OF THE GLOBE AT THE COAL EPOCH. 743 



feathery fronds; Sigillarias, with their fluted stems and enormous 

 matted roots; Oalamites, with their singular branches; Tree-ferns 

 and Coniferous plants, resembling the Norfolk Island Pine, and 

 towering a hundred feet above the rest of the forest. He also thinks 

 that the immense deposits of carbon at that epoch warrant the con- 

 clusion that the air contained a large amount of carbonic acid. These 

 conclusions are, of course, mere hypotheses. In regard to the. tem- 

 perature, it may be remarked that there is no evidence, from the 

 nature of the flora, of a marked increase of temperature at the coal 

 epoch. In New Zealand, which is in a latitude the same as that of 

 a great part of Europe, a very large proportion of the vegetation con- 

 sists of Acrogenous plants. Perns and their allies, in that country, 

 cover immense districts, replacing the grasses of other countries, 

 and giving a marked character to all the open land. Some of the 

 ferns attain a height of 30 or 40 feet, and occur in groups. Hemitelia 

 capensis, a Tree-fern found at the Cape, was also seen by Gardner, 

 at an elevation of 6000 feet, on the Organ mountains, thus showing 

 a capability of enduring a great range of climate, and warning us 

 against hasty conclusions on the subject of the temperature of the 

 world at the coal epoch. 



Dr. Hooker thinks that the prevalence of ferns may be regarded 

 as a probable evidence of the paucity of other plants, and the general 

 poverty of the whole flora which characterised the formation. He is 

 led to these conclusions from observing the mode in which the ferns 

 in Van Diemen's Land and New Zealand monopolise the soil, choking 

 plants of a larger growth on the one hand, and admitting no under- 

 growth of smaller species on the other. In New Zealand he has col- 

 lected 36 kinds of ferns on an area not exceeding a few acres ; they, 

 gave a most luxuriant aspect to the vegetation, which presented 

 scarcely a dozen flowering plants and trees besides. 



Some have supposed that the plants of the coal-fields have been 

 drifted into basins, others that they grew in the spots where they are 

 now found. Beaumont thinks that all the plants which are now 

 converted into coal grew in swampy islands, covered with a luxuriant 

 vegetation, which accumulated in the manner of peat-bogs ; that those 

 islands having sunk beneath the ocean, were there covered with sand, 

 clay, and shells, till they again became dry land, and that this opera- 

 tion was repeated in the formation of each bed of coal. The occur- 

 rence of stems of trees in an erect state (fig. 922) appeared to him 

 to confirm the view that the trees were in situ. Ansted says, that 

 although many trees are found in the Coal-measures in an erect or 

 highly-iaclined position, there is no reason for believing that they 

 grew on the spot where they are met with. He rather thinks that 

 they have been caught or stopped in their passage down a rapid stream, 

 and, like the snags in some of the great American rivers, have been 



