26 o 
Davie. — The Structure and 
in a systematic position among the Filicales. They have so many characters 
in common that it will be quite possible to consider their position first 
together, and then to see how far the characters in which they differ may in- 
dicate special affinities for each of them with other Ferns which they resemble. 
The ascending or upright stock which they show is shared by repre- 
sentatives of various groups of Ferns and cannot in itself be held as a strong 
diagnostic feature. It may none the less be noted that in Athyrium filix- 
foemina and in Nephrodium filix-mas the stocks are upright and of a similar 
type to that described for Peranema and Diacalpe. But in the latter pair 
there is a great development of sclerenchyma, which recalls the condition in 
the Cyatheaceae rather than that usual among the Polypodiaceae. In 
Athyrium and Nephrodium filix-mas definite sclerenchymatous sheaths are 
absent from the stocks. 
The presence of both hairs and scales removes the two from such forms 
as those included in the (i) Eudryopteris section of Dryopteris (Christensen, 
Tl) and relates them to (4) Last re a. 
In both cases the form of the leaf strongly suggests affinity with the 
Aspidieae. The tripinnate form is characteristic of the leaf in Nephrodium 
(Lastrea). The open, simply forked venation is a primitive feature, but it is 
shared by the members of the Eudryopteris section of Nephrodium and by 
numerous other members of the Polypodiaceae. 
The hairiness of the leaves suggests a relatively primitive state, while 
the glands in the case of Peranema show resemblances both to those in 
Eudryopteris and in Lastrea , 
When we look at the anatomical features we find that the general plan 
of the vascular system, with its advanced dictyostele, which shows no 
perforations but only leaf-gaps, and its subdivided leaf-trace, at once 
suggests affinity with Nephrodium filix-mas. The latter Fern appears, 
however, in the method of insertion of the leaf-trace strands on the gaps of 
the dictyostele to show an advance on the condition found in Peranema 
and Diacalpe . In these Ferns the leaf-trace bundles are inserted alto- 
gether on the lower half of the leaf-gap ; in Nephrodium filix-mas the 
bundles are more spread over the sides of the gap. As in both cases the 
median main bundle of the leaf-trace is inserted at the lower fork of the 
limbs surrounding the gap, it would seem that this condition has been 
derived from that seen in solenostelic and in the simpler dictyostelic types 
by a breaking-up of the continuous horseshoe-shaped leaf-trace into a series 
of separate strands. The histology of the bundles would seem to confirm 
this. For the adaxial face of the leaf-trace in various Ferns, as illustrated 
in such types as Loxsoma (Gwynne-Vaughan, ’01, Figs. 5, 6, 7) and 
Davallia Speluncae (Gwynne-Vaughan, ’03, Fig. 2 6), shows incurved edges. 
And the adaxial leaf-trace bundles in Peranema , Diacalpe, and Nephrodium 
filix-mas also show such incurved edges. Protoxylem groups appear in these 
