Bower. — Studies in the Phytogeny of the Filicales. 419 
These facts are not very distinctive, but they have their value. Taken 
quite generally, they show that there is an underlying common type of 
dermal appendage for the Ferns compared. Further, they indicate a pro- 
gression from a condition where the primitive hair is prevalent, to one 
where the derivative scale is prevalent ; and the latter state is found in 
those genera of our series which on other grounds of comparison are held as 
the more advanced, such as Woodwardia and Asplenium . 
Vascular Anatomy. 
All the Blechnoid Ferns and their derivatives that have been studied 
here show a dictyostelic structure of the axis, and a more or less divided 
leaf-trace. Thus they may all be held to have attained a relatively 
advanced state, and their comparison must proceed upon minor points. 
It is true that Plagiogyria has a dictyostele which still remains very close 
to solenostely, and that its runners may be solenostelic, while its leaf-trace 
is undivided (cf. Ann. of Bot., vol. xxiv, p. 428). But it is uncertain 
whether in Plagiogyria we really see a prototype of the Blechnoid Ferns. 
At all events it is by far the most isolated, as it is also the most primitive 
of the Ferns here considered. But of the true Blechnoid Ferns, de Bary 
(Comp. Anat., pp. 312-13, quoting from Stenzel, Nova Acta Acad. Leopold., 
Bd. 28) points out that in Blechnum spicant the vascular supply to a lateral 
axis arises as a single thread-like strand, while in Struthiopteris (. Matteuccia :) 
germanica it is tubular (solenostelic) in its lower region, and a similar tube- 
like system has also been seen in Diplazium giganteum. 
More recently, Chandler (Ann. of Bot., vol. xix, pp. 365-410, 
Pis. XVIII-XX) has investigated the vascular development of young 
plants of Blechnum gibbum and spicant , Doodia aspera , and Asplenium 
nidus and bulbiferum. These all show essential similarity. For young 
plants of Doodia the matter has been summed up by him (ibid., p. 403) in the 
statement that * the type of vascular elaboration met with in Doodia aspera 
is probably best, regarded as a short cut to the adult dictyostelic arrange- 
ment and that it is attained without the previous siphonostelic (or soleno- 
stelic) state — or with such a state very transitory indeed. It thus appears 
that a solenostelic structure is not altogether unknown in these Ferns, 
though they have all passed on to more complex arrangements in their 
mature state. 
All of these Ferns are dictyostelic, but the details may vary. A good 
central type is that seen in Blechnum Pater soni, where the transverse section 
shows eight leaf-gaps (p. 387). Just below the level of opening of each gap 
a root-trace is given off, by detachment of the middle portion of a meristele ; 
by this means the gap is opened, and at a higher level two equal leaf- 
trace strands are detached from the sides of the gap, and pass outwards as 
the leaf-trace. The systems of B. tabulare ) attenuatum , spicant , and 
