164 THE MEDALS OF CREATION. Cuap. VI. 
fied, and, when in situ, are invested with a friable carbona- 
ceous crust, of a glossy lustre, which soon falls to pieces on 
exposure to the atmosphere, so that cabinet specimens 
seldom retain any vestiges of it. When this coaly matter 
is removed, the surface of the silicified stem is seen to be 
traversed by numerous fine meandering grooves, and deep, 
tortuous channels, disposed in an irregular manner, in a 
longitudinal direction. These channels or vessels, which 
are generally lined with quartz crystals, give the surface 
that eroded appearace which suggested the specific name, 
erosa; but this term is inapplicable, for the perforations 
and sinuosities are not the effect of erosion, but result from 
the structure of the original. Polished sections, seen by 
transmitted light, are represented in Dr. Fitton’s memoir 
(Geol. Trans, vol. iv.); and Ihave had many slices ground 
as thin as possible, in the hope of detecting the characters 
of the vascular tissue. In one example there are indications 
of a cycadeous structure, which favour the conclusion, that 
the originals belonged to an extinct tribe of gymnosperms ; 
but in other specimens, bundles of vascular tissue, resem- 
bling those of palms, are apparent. 
Large water-worn stems of Hndogenites are occasionally 
washed out of the Wealden cliffs at Hastings, and in San- j 
down and Brook Bays, in the Isle of Wight. 
Fosstt CoNIFERZ. 
The other great natural order of Gymnospermous phane- 
rogamize,* the Coniferew, or cone-bearing—so named from 
the form of their fruit, of which the fir-cones and larch-juli 
are familiar examples,—comprise the extensive tribes of | 
Firs and Pines, and the Cypresses, Yews, Junipers, Cedars, 
&e., among which are the loftiest trees on the face of the 
globe. 
* Signifying, flowering plants with naked seeds. 
