394 



SPHENOPHVLLUM. 



[CH. 



thus giving rise to the tumid nodes referred to in the 

 diagnosis. The increased breadth at the nodes does not mean 

 that the xylem is broader in these regions, as it is in Calamite 

 stems. Small strands of vascular tissue are given off from the 

 three edges of the triangular stele (fig. 105^) at each node; 



Fig. 105. Sphenophyllum. 



A. Transverse section of young stem. 



B. Transverse section of the wood of a young stem; px, protoxylem; 

 a;, secondary xylem. (4 and B. Sphenophyllum plurifoliatum.) x 20. 



C. Transverse section of an old stem ; {S. insigne) ; a, phloem ; b, peri- 

 derm ; c, fascicular secondary xylem ; d, interfascicular secondary 

 xylem. x 9. (No. 914 in the Williamson Collection.) 



D. Longitudinal section of the reticulate tracheae and medullary rays; 

 r, r, r, of S. plurifoliatum. x 36. 



E. Similar section of S. insigne. x75. (D and E after Williamson and 

 Scott.) 



