THE ERIAN OR DEVONIAN FORESTS. 



79 



folk Island pine, than that of the modern yews. These 

 trees are chiefly known to us by their mineralised trunks, 

 which are often found like drift-wood on modern sand- 

 banks embedded in the Erian sandstones or limestones. 

 It often shows its structure in the most perfect man- 

 ner in specimens penetrated by calcite or silica, or by 

 pyrite, and in which the original woody matter has 



A B 



Fig. 29. — Vadoxylon Ouangondianum, an Erian conifer, a, Fragment 

 showing Sternberg pith and wood; a, medullary sheath; b, pith; 

 c, wood; d, section of pith, b, Wood-cell; a, hexagonal areole; 

 6, pore, c, Longitudinal section of wood, showing, a, areolation, and 

 b, medullary rays, d, Transverse section, showing, «, wood-cells, and 

 6, limit of layer of growth, (b, c, d, highly magnified.) 



been resolved into anthracite or even into graphite. 

 These trees have true woody tissues presenting that beau- 

 tiful arrangement of pores or thin parts enclosed in cup- 

 like discs, which is characteristic of the coniferous trees, 

 and which is a great improvement on the barred tissue 

 already referred to, affording a far more strong, tough, 



