Ophioglossales. 265 
Oar general conclusion must be then, that the theory of the 
typical Osmundaceous stele as a reduced type of structure, a theory 
for which there was never a really strong case, has been rendered 
much less probable by the work of Gwynne-Vaughan and Kidston, 
and that while it is conceivable that the type of structure seen in 
Osmunda cinnamomea has been reduced from the type of O. 
skidegatensis, no sufficient reason has been assigned for such a 
reduction, any more than for the supposed further reduction to the 
type of O. regalis. Certainly the appearance of such a form as O. 
cinnamomea is by no means completely explained, but on the whole 
fewer difficulties are involved by regarding it as a progressive than 
as a retrogressive type. 
Ophioglossales. 
There is no need to discuss in this place the various affinities 
that have been suggested for this very isolated group of plants. 
The outstanding morphological character of the group is of course 
the forking of the leaf into a fertile (ventral, adaxial) and a sterile 
(dorsal, abaxial) limb. The general feature of the group which 
Fig. 92. Steles of Ophioglossales. A.— Helminthostachys, after Farmer 
and Freeman. B .—Botrychium Lunaria. C .—Ophioglossnm vulgatiun, after 
Hollc. /.<., leaf-trace; l.g., leaf-gap; R., Root stele. 
interests us most from the anatomical point of view is their 
megaphylly and their possession of a hollow vascular cylinder which 
is broken by the departure of leaf-traces (Fig. 92). It will only be 
necessary to treat the leading features of the group quite shortly. 
