THE CARBONIFEROUS FLORA. 



113 



the thin bark and firm wood with which we are familiar 

 in our modern trees, it has a hard external rind, then a 

 great thickness of celluldr matter with rope-like bands of 

 fibres, constituting an inner bark, while in the centre is 

 a firm, woody axis of comparatively small diameter, and 



Fig. Zi.—SigUlwria Lorwayana, Dawson, a. Zones of fruit-soars. 6, Leaf- 

 scar enlarged, o. Fruit-soar enlarged. See appended note. 



somewhat intermediate in its structures between that of 

 the Lepidodendra and those of the cycads and the taxine 

 conifers. Thus a great stem, five feet in diameter, may 

 consist principally of cellular and bast fibres with very 

 little true woody matter. The roots of this tree are 



