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GEOLOGICAL MEMOIRS. 



Coal-flora has been introduced into the distinct floras of the Trias and 

 of the Lias, and that only in one spot, while all the land in the neigh- 

 bourhood had a vegetation which exhibits so strikingly the connec- 

 tion in the development of the vegetable creation. This hypothesis 

 so contradicts all our experience of the history of its development, 

 that it cannot longer be supported ; and the more, when we consider 

 that the Coal-flora as far as it is known had the same characters over 

 the whole surface of the earth, and at its most distant parts the very 

 species were partly identical. Of the Lias it is not yet known 

 whether its plants had so wide a distribution ; but we do know (and 

 we owe this important fact to Sir R. I. Murchison) that in much 

 later times, in the Nummulitic Formation, a great similarity of the 

 molluscous fauna obtained throughout Europe all the way to India, 

 and that the same characters may be traced from Spain and Morocco 

 to the Brahmaputra in India, and from the northern slope of the 

 Alps to Egypt. 



It has of late been occasionally asserted that plants do not present 

 discriminating geognostic characters, so that we are further called upon 

 to assume that they were subject to a law of development different to 

 that of animals. But before admitting that different laws subsisted for 

 the two natural kingdoms, better grounds must be adduced than have 

 been hitherto brought forward. Sir R. Murchison instances the 

 Calamites arenaceus, as a proof that, in determining the age of a 

 deposit, the presence of certain plants is not so conclusive as that of 

 animals * : but here there is an oversight ; for Brongniart, who is 

 quoted, never speaks of that plant as occurring in the old Coal-for- 

 mation, but only in the Trias. Moreover, it must not be overlooked, 

 that identifications founded only on parts of the stem are not so satis- 

 factory as those deduced from foliage : consequently Calamites and 

 Equisetaf, which are principally known from small parts of the stem, 

 are less proper for certainty of comparison and for drawing conclu- 

 sions. But this arises from the state of preservation of those plants, 

 and in nowise from peculiar species not being restricted to determi- 

 nate periods. Whenever the characteristic organs of plants are well 

 preserved, they are as good indications of the age of the beds as ani- 

 mals ; — a truth which is more and more established, the more plants 

 are studied and made known to us. The conclusions, however, which 

 we draw from them will have the more weight when they are derived, 

 not from one or two isolated species about whose identification doubts 

 may be entertained, but from the union of several species and the 

 aspect of the entire flora, as is the case with the flora of those an- 

 thracitic schists. 



When Sir Henry Be la BecheJ undervalues the certainty of geo- 

 * Loc. cit. p. 178. 



f [See observations on Calamites, Equiseta, and C. arenaceus, supra, Part I. 

 pp. 189, 190.— Ed.] 



% Biblioth. Univ. de Geneve, Oct. 1849. [This has reference to an Abstract of 

 Sir H. De la Beche's remarks on the Petit-Cceur Anthracite and the dispersion 

 and accumulation of plants, as given in his Presidential Address 1849 (Q. J. G. S. 

 vol. v. pp. xxxviii-xlii). But Sir Henry's observations only apply to fossil plants 

 as indications of the climate at the time when, and on the spot where, they were 

 accumulated. — Transl.] 



