Bower. — Shidies in the Phytogeny of the Filicates . VI. 33 
divided leaf-traces, like N. Filix mas, but greatly extended. Taking the 
characters generally into consideration, the near relation of these Ferns 
to one another, and their reference to an Aspidioid affinity, are probably 
correct. 
All the Acrostichoid types so far considered (excepting Trismerid) may 
thus be referred in origin to some indusiate source. There remain for 
consideration Elaphoglossum , Leptochilus , Photinopteris , Platy cerium, and 
Cheiropleuria. These were probably derived from non-indusiate sources, 
which will now be discussed, together with their relations one to another. 
In the first place, Elaphoglossum may be segregated from the rest on the 
point of its venation, as already described above (p. 38). For reasons there 
given the genus may be held as distal in a series connected with such 
a form as Metaxya. The ultimate origin would probably be from some type 
like Gleichenia , with protostelic rhizome, highly branched leaves with 
undivided leaf-trace and open venation, dermal hairs, and relatively few 
large sporangia grouped in superficial sori. The next step is illustrated by 
Metaxya , with solenostelic rhizome, simply pinnate leaves, undivided leaf- 
trace and open venation, dermal hairs, and more numerous, smaller 
sporangia in sori sometimes elongated or plural upon the vein. Next Syn- 
gramme, with leaf rarely branched, usually quite simple, divided leaf-trace, 
and venation showing irregular fusions, dermal hairs, and the sori continuous 
along the veins. Finally, Elaphoglossum , with rhizome containing a soleno- 
stele with occasional perforations, leaves entire, highly divided leaf-trace and 
reticulate venation without blind twigs, dermal scales, and numerous 
Polypodioid sporangia extended over the whole lower surface. The 
parallelism of the progressive characters confirms the relations suggested, 
some of which had already been indicated by other writers on general 
systematic grounds. The genera named may be held to indicate a phyletic 
progression, and they may be designated the Metaxyoideae. 
The remaining Acrostichoid genera are Cheiropleuria , Platycerium , 
Leptochilus , and Photinopteris. They have in common a reticulate venation 
with blind vascular twigs ending within the relatively small areolae. The 
Venatio Anaxeti 1 is the central type for them all, though they differ in 
detail. There is no indication of any abortive indusium in relation to their 
superficial soral areas. Of relatively primitive Ferns with such characters 
the living genus Dipteris provides the obvious line of comparison. It is 
recognized as the surviving representative of the family of the Dipteridinae, 
which included many forms of the Mesozoic period, characterized by various 
and elaborate leaf-construction, but still with the same type of venation, and 
with superficial, non-indusiate sori. 2 It is now suggested that the living 
genera above named, together with certain Polypodioid genera, such as 
1 Luerssen, Rab. Kryp.-Fl., Band iii, Fig, 22, p. 18. 
2 See Seward, Fossil Plants, vol. ii, pp. 380-94. 
D 
