62 THE MEDALS OF CREATION. Cuap. IV. 
genus of the fossil plants which the geologist has to examine ; 
hence, in most instances, a general idea only can be obtained 
of the nature of the original.* To facilitate the study of 
Fossil Botany they offer some practical suggestions, which 
have served as the basis of the following directions for the 
investigation of vegetable remains, and which the previous 
remarks will, we trust, render intelligible. 
1. The Trunk, or Stem.—Examine if the wood in a trans- 
verse section be disposed in concentric circles (as Plate V. 
Jig.4): if so, it belonged to an exogenous tree : if, on the con- 
trary, the wood appears deposited irregularly in spots (Lign. 1, 
jig. 4), then the original was endogenous. If a transverse sec- 
tion show remains of sinuous, unconnected layers, resembling 
Lien. 2. SECTIONS OF FERN-STEMS. 
Transverse sections (half the diameter) of two stems of recent Arborescent Ferns, 
to show the zone of woody fibre disposed in arcs. This structure is seen in the 
silicified trunks from Chemnitz. 
ares with their ends directed outwards, and of a solid struc- 
ture, and imbedded among looser tissue, then it belonged to 
an arborescent fern ; see the subjoined figures (Lign. 2). 
If the stem be in a state of preservation that will admit 
of the slicing or chipping off a piece for microscopical inves- 
* Foss. Flor. vol. I. p. xxvi. 
