THE CARBONIFEROUS FLORA. 



131 



Europe and America. We sometimes, though rarely, 

 find their stems showing structure. In this case we have 

 a large cellular pith, often divided by horizontal parti- 

 tions into flat chambers, and constituting the objects 

 which, when detached, are called SUrnbergm (Fig. 62). 

 These Sternbergia piths, however, occur in true coni- 

 fers as well, as they do 

 in the modern world 

 in some trees, like our 

 common butternut, of 

 higher type ; and I 

 showed many years ago 

 that the Sternbergia 

 type may be detected 

 in the young twigs of 

 the balsam -fir (Abies 

 lalsamifera). The pith 

 was surrounded by a 

 ring of scalariform or 

 barred tissue, often of 

 considerable thickness, 

 and in young stems so 

 important as to have 

 suggested lycopodia- 

 ceous affinities. But as 

 the stem grew in size, 

 a regular ring of woody 

 wedges, with tissue hav- 

 ing rounded or hex- 

 agonal pores or discs, 

 like those of pines, was developed. Outside this was a 

 bark, often apparently of some thickness. This struct- 

 ure in many important points resembles that of cycads, 

 and also approaches to the structure of Sigillaria, while 

 in its more highly developed forms it approximates to 

 that of the conifers. 



FIG. 5%.Cordaites (Dory cor daites), 

 Grand 7 Eury, reduced. 



