ROOM I. WEALDEN PLANTS. 49 



at each end ; others are of a depressed clavated form, like 

 some of the Cacteae or Euphorbise. These fossils are gene- 

 rally transmuted into a hard and fine siliceous grit, and, 

 when in situ, are invested with a friable carbonaceous bark of 

 a glossy lustre, which soon falls to pieces on exposure to 

 the atmosphere ; so that cabinet specimens seldom retain 

 any vestiges of this integument. When this crust of coaly 

 matter is removed, the surface of the silicified stem is seen to 

 be traversed by numerous fine meandering grooves, and deep, 

 tortuous, tubular 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 appearance whence the specific name erosa was 

 derived : they are not, however, the effect of erosion, but of 

 the original structure of the plant ; they traverse the sub- 

 stance of the stems, and although no symmetrical arrange- 

 ment is apparent, this anomaly is probably attributable to the 

 changes which the vegetable organization has undergone during 

 its mineralization. In one instance (a specimen from the Weal- 

 den of the Isle of Wight), bundles of vascular tissue, ar- 

 ranged in a flexuous zone round the margin of the cylinder, 

 are observable in polished sections under the microscope ; 

 the structure approaches more nearly that of the Cycadese 

 than of the Euphorbiacese, with which some botanists have 

 associated these enigmatical plants of the Wealden flora. 1 



DRACAENA (D. Benstedi). Case E. In the lowest depart- 

 ment of the same case are fragments of a large fossil stem 

 allied to the Draccena, or Dragon-blood Tree, discovered by 

 Mr. W. H. Bensted, of Maidstone, in a quarry of Kentish Rag, 

 near that town ; a locality to which we shall more particularly 

 allude in the sequel. The largest portion is two and a half 

 feet in length, and eight inches in diameter ; the surface is 

 marked with interrupted annular ridges, indicating amplexi- 

 caul leaves. These fossils were found associated with drifted 

 coniferous wood, and bones of turtles and iguanodons. 



Medullosce. Case />. In the lower division, beneath the 

 Lepidostrobi, there are many specimens, some cut and po- 



1 Figured in " Fossils of Tilgate Forest," PI. III.; " Geology of the S.E. 

 of England," PL I. : by Dr. Fitton, in " Geol. Transactions," vol. ir. 



