﻿xl PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



and imperfect, and in which some whole genera or families seem to 

 have no natural place. But if we seek to classify plants according to 

 a linear arrangement, ascending gradually from the lichen to the lily 

 or the rose, we encounter incomparably greater difficulties. Yet the 

 doctrine of a more highly-developed organization in the plants created 

 at successive periods presupposes the admission of such a graduated 

 scale. 



There can, however, be no dispute that the cryptogamous plants 

 are the least perfect, a class to which the marine vegetation almost 

 entirely belongs. The sea, it is true, produces some flowering plants, 

 such as Zostera and Caulinia, but they are among the least-developed 

 of the phaenogamous tribe. If then the oldest fossiliferous strata, the 

 Silurian and the greater part of the Devonian, contain exclusively ma- 

 rine plants, we may attribute the low scale of their organization to the 

 pelagic nature of the deposits, and our not having yet found the deltas 

 of the then existing rivers into which we might expect land plants to 

 have been drifted. Even the lacustrine genera of plants which are 

 truly subaqueous, such as Chara and Potamogeton, are commonly re- 

 garded by botanists as holding an inferior rank to the great mass of 

 the phaenogamous vegetation of the land, — a circumstance not to be 

 lost sight of, when we are considering the scale of organization in re- 

 lation to geological epochs. 



By far the greater number of the land plants hitherto referred to 

 the Devonian strata on the continent of Europe, especially those in 

 France, in the department of La Sarthe, and various parts of Brittany, 

 have been lately shown (in 1850) by M. de Verneuil to belong to the 

 carboniferous series. The same maybe said of the species of Lepidoden- 

 dron, Knorria, Calamite, Sagenaria, and other genera recently figured by 

 M.F. A.Roemer from the formation called Grauwacke aPosidonomyes 

 in the Hartz. We may treat therefore of the flora of the coal-measures 

 as the first or oldest known to us, from which we can gain a true insight 

 into the terrestrial vegetation of the palaeozoic epoch. More than 700 

 plants have been enumerated by some botanists as belonging to the 

 carboniferous strata; and M. AdolpheBrongniart, after considerably re- 

 ducing the number of species, in consequence of many having been 

 founded on the leaves, stems and fruit of one and the same plant, still 

 reckons at least 500 species, one half of which are ferns. The greater part 

 of the remainder belong to the dicotyledonous gymnosperms, of which 



