454 



PALEOBOTANY. 



America. In tlie genus Sphenoptcris, the leaflets are narrow 

 towards their bases, often assuming a wedge-like form, the 

 nervures dividing in a pinnate manner from the base. 



Fig. 7Ci6.—Odontopteris Sclilotheimii. Carboniferous of Europe and North America. 



Lastly, in the genus ITymenopliyllitcs the frond exhibits 

 a general resemblance to Sphenopteris, but the margin is 

 divided into lobes, into each of which a single nervure is 

 continued. 



h. Calamitcs. — Amongst the commonest and most charac- 

 teristic of the plants of the Carboniferous period are the 

 striated fossils which are known as Calamites. Long as 

 these have been known, and carefully as they have been 

 studied, there is still no unanimity of opinion as to the 

 affinities of these plants. It is now, however, generally ad- 

 mitted that the Calamitcs are truly referable to the Equisctacecc, 

 and that they may be regarded as gigantic Horse-tails — 

 though they differ in many respects from any existing forms. 

 The Calamitcs were " slender, ribbed, and jointed externally, 

 and from the joints there proceeded, in some of the species, 

 long, narrow, simple branchlets ; and, in others, branches 

 bearing whorls of small branchlets or rudimentary leaves. 

 The stem was hollow, with thin transverse floors or dia- 

 phragms at the joints, and it had no true wood and bark, 

 but only a thin external shell of fibres and scalariform vessels. 



