Ophioglossales. 269 
direction, though the individual genera are too peculiar and isolated 
to make it reasonable to lay very much stress on the point. 
There is no evidence of internal phloem in any member of the 
group, and the type of Helminthostachys is probably derived from 
that of a mesarch protostele which has acquired a ground-tissue 
pith. This view leaves us free to relate the Ophioglossales to 
primitive Ferns, Cycadofilices, Sphenophyllales or Lycopods, or to 
the common ancestors of all these groups. The line of evolution 
within the group, from the meagre evidence afforded by the existing 
types, is to some extent parallel, with that of the Ferns, but in other 
respects nearer the Cycadofilices. The marked megaphylly of the 
Ophioglossales also tends, of course, on the views expressed at the 
beginning of the present course of lectures, to relate them to one 
or both of these last-mentioned groups rather than to the micro- 
phyllous forms. Nevertheless, the morphological resemblance of 
the sporophylls to the Sphenophylliun-Psilotum type cannot be 
entirely ignored, and the net result of a consideration of the Ophio¬ 
glossales from all points of view, is a strengthening of the tendency 
to relate all these groups, 1 so widely divergent at the present day, 
to some very remote, but essentially megaphyllous ancestor. 
1 With the possible exception of the Lycopods. 
