CHAPTER IV 



SPHENOPHYLLALES 



Sphenophylleae ; Cheirostrobeae ; Pseudoborniales 



So far, we have been endeavouring to extend our 

 knowledge of a class already familiar to us, by the 

 study of its extinct representatives. We now go on 

 to fill in a gap in the natural system in a different 

 way, by the description of a group which appears so 

 remote from any recent plants, that it is only quite 

 within the last few years that its probable affinity with 

 an isolated existing family (the Psilotaceae) has been 

 detected. The class in question — that of the Spheno- 

 phyllales — was not, so far as our present knowledge 

 shows, an extensive one, but it is of great phylogenetic 

 interest. 



I. Sphenophylleae 



i. Sphenophyllum — Vegetative Organs. — The exter- 

 nal aspect of the various species of Sphenophyllum has 

 long been familiar to palaeobotanists ; the specimens, 

 when preserved in the form of impressions, are often 

 among the prettiest of the Carboniferous remains. The 

 genus, which is nearly co-extensive with the family 



86 



