84 M. De Candolle on Fossil Vegetahles. 



formed the wood and the bark. The shape is in no respect 

 altered. Leaves, however, are recognised more as mere impres- 

 sions, and may be separated, of a black or grey colour, from the 

 rest of the stone. 



That we may profitably compare these remains with species 

 wliich are now flourishing on the earth's surface, we must select 

 from these latter specimens of the same parts, and consequently 

 of the trunks and leaves. The arrangement of the ligneous 

 layers of dicotyledonous plants, and that of the fibres of niono- 

 cotyledonous also, maybe easily recognised in fossils, if we make 

 the comparison with specimens taken from trunks of these two 

 classes. And this shews the utility of those collections of wood, 

 where the bark and the wood are in their natural connection, 

 and where a fixed nomenclature may assist in the comparison. 

 The texture of the wood also, made more evident by the micro- 

 scope, and more distinct still by having the surface polished, is 

 also a great help in recognising the analogy between a fossil re- 

 main, and any of the classes of existing vegetables. 



JBy a little management of this sort, it but rarely ha|)pens that 

 we cannot discover some analogy, which enables us to associate 

 tlie fossil with some presently existing family. Sometimes a 

 great number of specimens ally themselves with forms which are 

 now exceedingly rare.* 



2. On the Nomenclahire of Fossil Plants. — The nomenclature 

 of fossil vegetables is as much as possible founded upon their 

 alliance with living ones. Originally they sometimes received 

 names, whose termination in lithis indicated that they were fos- 

 sil ; and it is perhaps to be regretted, that this custom has not 

 been continued, and so all risk of compounding fossil and living 

 plants been avoided. At present, all that is done is to name 

 the genera and species in the same manner that living plants are 

 named, and they are referred, either with certainty, or with 

 more or less hesitation, to the great classes and families now 

 living. Thus Lepidodendron insigne is a species of a fossil 

 genus of the family Lijcopodiacea, and Equisetum columnare, 

 is a fossil species of the living genus Equisetum, In this last 



• M. De Candolle appears to be unacquainted with the interesting obser- 

 vations which have been made on fossil plants at Edinburgh — Edit. 



