preserved In Chalcedony, 517 



to which I have already referred, several species are actually described 

 as having been well ascertained ; and vv^hen we read of two plants 

 in particular, whose characters are so strong and so decided as 

 Lichen d'gitatus and Lichen rangiferinus, v/e cannot suppose it 

 possible that he or any other observer could have been deceived. 

 The execution of the plates which accompany his paper has unfor- 

 tunately not rendered justice to the apparent accuracy of his obser- 

 vations. 



It will be seen on inspection either of the specimens or of the 

 drawings, that probably all the plants belong to the Cryptogamia 

 class, and are limited to certain species of them. The explanation 

 of this is sufficiently obvious. It is evident that the siliceous depo- 

 sitions which contain these remains must have been formed in ca- 

 verns and clefts of rocks, situations only occupied by a few species 

 of this class of plants, and these chiefly Byssi, Confervse, Junger- 

 manniae, and the Mosses most commonly so called, plants which re- 

 quire very little light. All the specimens which I have figured will 

 accordingly be found to belong to one or other of these families, 

 with the exception of a few which appear to be fragments of plants, 

 and which I have been unable from their mutilated state to compare 

 with any known species. 



It may be asked whether the plants thus preserved are specimens 

 of existing species, or whether they are, like those found entangled 

 in the secondary strata, the remains of a former set of organized 

 beings. The limited number of the specimens which I possess, and 

 the obscurity which attends not only these remains but the present 

 living species, prevents me from attempting an answer to this question; 

 on botanical evidence, and on my own knowledge. But the obser- 

 vations of Daubenton appear sufficient to decide that in some instances 

 at least they consist of existing species. Since too the formation of 



