.398 



SPHENOPHYLLUM. 



[Cl 



but it evidently bore foliage in which the leaves were deeply] 

 divided, as in Sphenophyllum trichomatosum (fig. 110, B). 



Fig. 106. Sphenophyllum plurifoliatum, Will, and Scott. 



From a photograph by Mr Highly from a section in the Williamson Collec- 

 tion (no. 899). x27. 



In this species there are no canals at the angles of thel 

 primary xylem, and there are fewer spiral tracheae than in] 

 8. insigne. The tracheae of the secondary w^ood have niimerous\ 

 small pits on the radial walls, and the medullary rays arej 

 chiefly composed of parenchymatous cells, which appear inj 

 transverse section as groups of cells between the truncated 

 angles of the tracheae. The characters are fairly well seen inj 

 the xylem portion of a stele shown in fig. 106. The fascicular! 

 wood includes some rows of parenchymatous medullary-ray] 

 cells in addition to the characteristic groups, as seen in the' 

 figure. A slightly oblique transverse section of a stem is often 

 convenient in the interpretation of histological features ; one of 

 the sections of >S^. plurifoliatum in the Williamson collection 

 (no. 893), which has been cut somewhat obliquely, shows very 

 clearly the differences in pitting exhibited by the different 

 xylem elements. 



