214 Successive Geological Developynent. 



tribe. If then the oldest fossiliferous strata, the Silurian 

 and the greater part of the Devonian, contain exclusively 

 marine plants, we may attribute the low scale of their organi- 

 zation 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 sub- 

 aqueous, such as Chara and Potamogeton, are commonly re- 

 garded by botanists as holding an inferior rank to the great 

 mass of the phsenogamous vegetation of the land, — a circum- 

 stance not to be lost sight of, when we are considering the 

 scale of organization in relation to geological epochs. 



By far the greater number of the land plants hitherto re- 

 ferred 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 shewn (in 

 1850) by M. de Verneuil to belong to the carboniferous series* 

 The same may be said of the species of Lepidodendron, Knor- 

 ria, Calamite, Sagenaria, and other genera recently figured 

 by M. F. A. Boemer from the formation called Grauwacke d 

 Fosidonomyes 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. Adolphe Brongniart, after con- 

 siderably reducing 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 some are 

 true Coniferte ; and a much larger proportion belong to an 

 anomalous family, departing very widely from any living type, 

 to which the Sigillaria, Noeggerathia, and Asterophyllite are 

 referred. They united some of the characters now peculiar 

 to the Cryptogamia and dicotyledons respectively. It is very 

 remarkable that none of the exogens of Lindley or dicotyle- 

 donous angiosperms of Brongniart, which comprise four- 

 fifth^ of the living flora' of the globe, have yet been discovered 



