PETRIFACTIONS AND THEIR TEACHINGS. 



CHAP. I. 



from the calciferous grit of Tilgate Forest ; and they form 

 a highly instructive series, comprising portions of stems 

 scored with the imprints of the petioles, the internal im- 

 bricated axis, leaf-stalks, and indications of the foliage and 

 flower-buds. 



The stem of the Clathraria 

 is composed of an axis or in- 

 ternal column, the surface of 

 which is covered with reticu- 

 lated fibres. The large branched 

 fossil lying on a slab of stone 

 in the middle of the case, is 

 the finest specimen of this part 

 hitherto obtained: it was dis- 

 covered, with bones of the 

 Iguanodon, in a quarry near 

 Cuckfield, Sussex, in 1820. 

 The axis is invested with a very 

 thick bark formed of the con- 

 solidated bases of the leaf- 

 stalks, the insertions of which 

 are rhomboidal and transverse. 

 The outer surface of the bark is 

 in consequence marked with elevated lozenge-shaped cicatrices, 

 separated from each other by a marginal furrow, which is 

 suiTounded by a parallel ridge or band of a fibrous structure. 

 The cortical portion of the stem is in general converted into a 

 cylinder of stone, which in some instances will separate from the 

 axis. There is a beautiful specimen of this kind in the case ; and 

 likewise one in which the axis projects, and is surrounded by 

 the bark. 1 The axis is solid, and has its surface strongly 

 marked with interrupted reticulated ridges. This surface has 

 generally patches of vascular tissue adhering to it ; and on 

 some parts there are deep pits or lacunae, which probably con- 

 tained a resinous secretion. I have spared neither trouble 

 nor expense in endeavouring to detect the organization of this 

 plant ; scores of sections of stems have been made and exa- 

 mined microscopically, but very few specimens exhibit any 



LIGN. 15. WATERWORN SPECIMEN, 

 SHOWING THE EXTERNAL SURFACE 

 OF THE STEM OF CLATHRARIA L\ r - 

 ELLII. WEALDEN. 



(| nat. size.) 



1 This, and the large branched specimen of the axis, were first 

 described and figured in my " Fossils of Tilgate Forest," PI. I. 



