73 2 Gwynne- Vaughan . — Observations on the 
If the solenostele and the Lindsaya-type of stele are to be 
regarded as the most primitive types of vascular arrangement 
in the Polypodiaceae, as suggested above (p. 71 7), it must at 
the same time be admitted that these primitive characters 
do not run parallel with Professor Bower’s division of the 
order into Gradatae and Mixtae. Bower himself, however, 
supports the view that several different lines of descent may 
be represented within the Polypodiaceae alone 1 , and it is very 
probable that a more or less similar primitive type of vascular 
arrangement might occur in the primitive members of each 
line of descent. It follows that those genera in which the 
solenostele, or the Lindsaya-type of stele, is predominant may 
be regarded as relatively primitive, at any rate within their 
own particular family. The prevalence of the primitive types 
of stele in the various genera and subgenera may be summed 
up as follows. 
All the species of Dennstaedtia (regarded by Hooker in the 
‘ Synopsis Filicum ’ as a section of Dicksonia) that have 
hitherto been examined prove to be essentially solenostelic. 
It must be noted, however, that in D. rubiginosa the soleno- 
stele is not quite typical, and that additional internal vascular 
strands are also present. 
Microlepia , including Saccoloma , is placed in the ‘ Synopsis 
Filicum ’ among the Davallias, and, apart from the fact that 
additional internal vascular strands are present in the Sacco- 
lomas (cf. p. 703), all the species that have been examined are 
typically solenostelic with two exceptions only. Of the ex- 
ceptions, Davallia ciliata is dorsiventrally dictyostelic, and is 
clearly out of place among the Microlepias 2 . It is placed by 
1 Bower, Studies in the morphology of spore-producing members, no. 4, Phil. 
Trans. Roy. Soc. London, Series B, vol. cxcii, p. 123, 1899. 
2 Professor Bower has been kind enough to examine the sorus of this species for 
me, and he finds that ‘ the receptacle is almost flat, and the sporangia of various 
ages are intermixed ; successive ones being interpolated without order between 
those already there. The older sporangia are long stalked, so as to raise their 
heads above the younger. There appears to be no regularity of orientation. The 
annulus is vertical. All these characters stamp it as one of the Mixtae, and it 
should find its place elsewhere than among the Microlepias.’ 
