SPHENOPHYLLEAE 



93 



39. This peculiar structure of the wood is found both 

 in the English (Figs. 38 and 39) and in the French forms 

 (Fig. 36, D), but is not common to the whole genus, 

 as we shall see presently. The elements of the wood 

 are arranged with the greatest regularity (Fig. 38). 

 There is a marked difference in size between the second- 

 ary elements found opposite 

 the sides of the primary wood, 

 and those corresponding to its 

 angles ; the former are much 

 the larger (see Fig. 38). In 

 the small-celled wood oppo- 

 site the angles there is an 

 approach to the formation of 

 continuous rays. 



In the best - preserved 

 specimens we find, immedi- 

 ately beyond the wood, the 

 delicate tabular cells of the 

 cambium itself, sometimes 



Fig. TQ.Sphenofikyllumplurifohatnm. 



mOSt distinctly Shown, and Radial section through pait of 



. secondary wood, showing pitted 



beyond thlS We COme tO a tracheides and parenchyma (?•). X50. 



r it.- 11 J _„JJ„1K, P/u/. Trans., W. and S. Will. Coll. 



zone of thin-walled radially- 884 

 arranged tissue, which can 



only be interpreted as the phloem (see Fig. 38). 1 

 Beyond this again, in older stems, lies a wide band 

 of firmer tissue, also radially arranged, which we must 

 regard as internal periderm (Fig. 38). If we examine 

 a comparatively young stem of Sphenopkyllum, we find, 

 in many cases, a very distinct beginning of periderm- 



1 For more complete illustrations of the various tissues, see Williamson 

 and Scott, I.e. 



