THE BRIAN 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 



V 



Fio. 29. — Dadoxylon Ouangondianum, an Erian conifer, a. Frngraent 

 Bhowinjr Sternberfria pi^li and wood: a, naedullary slieatli; ft, pith^ 

 c, wood ; d. section of pith, b, Wood-cell ; a, hexatronal areola | 

 i, pore, c, Lonj,'itudinal section of wood, showinj^, a, areolation, and 

 b, medullary rays, d. Transverse section, sliowintr, a, wood-cells, and 

 6, limit of layer of growth, (b, c, u, 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- 

 iike 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. 



m 



