THE CARBONIFKROUS FLORA. 



137 



ure which, as I haye already mentioned, appears on a 

 minute scale in the twigs of the flr-tree, and that some- 

 times casts of these piths in sandstone appear in a separate 

 form, constituting what hare been named Sternbergice or 

 ArtisicB. As Kenault well remarks with reference to 

 Cordaites, the existence of this chambered form of pith 

 implies rapid elongation of the stem, so that the Cordaites 

 and conifers of the coal-formation were probably quickly 

 growing trees (Fig. 62). 



The same general statements may be made as to the 

 coal-vegetation as in relation to that of the Erian. In 



Fig. 62. — Sterribergia pith of Dadoxylon, A, Specimen (natural size), 

 showing remains of wood at o, a. b, Junction of wood and pith, mag- 

 nified. 0, Cells of the wood of do., a, a; b, medullary ray; e, areo- 

 lation. 



the coal period we have found none of the higher ex- 

 ogens, and there are only obscure and uncertain indica- 

 tions of the presence of endogens, which we may reserve 

 for a future chapter ; but gymnosperms abound and are 

 highly characteristic. On the other hand, we have no 

 mosses or lichens, and very few Algae, but a great num- 

 ber of ferns and Lycopodiacese or club-mosses (Fig. 63). 

 Thus, the coal-formation period is botanically a meeting- 

 place of the lower phaenogams and the higher cryptogams, 

 and presents many forms which, when imperfectly known, 

 have puzzled botanists in regard to their position in one 

 or other series. In the present world, the flora most akin 



