FOSSIL VASCULAR CRYPTOGAMS 



129 



measures. Very little is known of their stem, which appears, however, 

 to have resembled that of the Calamaries. 



More doubt rests on the affinity with the Equisetaceae of the group 

 of Sphenophylle^. The remains of Sphenophyllum (Brongn.) are 

 found in abundance in the Carboniferous formation, but do not come 

 down to more recent times 

 than the Lower Permian. 

 The stem is divided into 

 distinct nodes and inter- 

 nodes, the latter usually 

 marked with conspicuous 

 ridges and furrows, which 

 are not alternate in adja- 

 cent internodes, but pass 

 continuously through the 

 nodes. At the swollen 

 nodes are whorls of leaves, 

 with occasional axillary 

 branches. Each whorl ap- 

 pears to consist always of 

 six leaves or of some mul- 

 tiple of six. They are ses- 

 sile, and obcuneate from a 

 narrow base, sometimes 

 denticulate and bifid at the 

 apex, but are not in any 

 degree connate. Each leaf 

 contains a number of 

 simple or dichotomous 

 ' vascular ' bundles. In 

 the centre of the stem is 

 a triangular bundle com- 

 posed of scalariform tra- 

 cheides, to which some 

 authorities add spiral tra- 

 cheides and others with 

 bordered pits ; the bundle 

 change. 



Fig. 



-I, 2, Fructification and branch of AsieropkyU 

 lites ; 3_, 4, fructification and brancli of Annularia ; 5, 

 6, fructification and branch of Sphenophyllum, (After 

 Carruthers.) 



passes through the node without material 

 This is often surrounded by some layers of secondary wood ; 

 the greater part of the stem, on transverse section, is occupied by a 

 small-celled parenchyme. 



The fructification of Sphenophyllum consists of cylindrical cone- 

 like spikes resembling those of Calamites. It is composed of whorls 



