Bower.—Studies in the Phytogeny of the Filicales . 443 
Passing to the leaf itself, the simply pinnate form gives no distinctive 
point for comparison, but the serration suggests that it has been condensed 
from some more complex prototype. The simply forked venation points 
clearly to a primitive position, though, as is well known, many Ferns of 
advanced affinities still show it. 
The existence of buds and stolons is a widespread feature in Ferns, 
but the peculiar relation which they bear to the leaf in Plagiogyria pycno- 
phylla and glaaca resembles in near degree that seen in the Hymeno- 
phyllaceae ; in them, as has been seen, the bud is subtended by the leaf, 
but there is some variation in the position of the bud relatively to the 
leaf-base, and in some cases it appears to be borne upon the leaf; the 
condition of Plagiogyria would then be only a case of the further removal 
of the axillary bud from the basal position ; as already suggested, this may 
be a consequence of the close aggregation of the leaves upon the axis, which 
would necessitate a more distal position for the accessory bud. It is true 
many other Ferns have buds associated with their leaf-bases, but none of 
them seem so nearly to correspond to what is seen in Plagiogyria as do 
the Hymenophyllaceae. 
Turning to the anatomical features, it has been seen that the stolons 
show at their base a structure that is solenostelic, or even protostelic; in 
the absence of young plants this may be taken as evidence of a primary 
structure of the axis, such as is seen in various primitive types of Ferns. 
The mature axis shows a condition of dictyostely, though this is not of 
a high grade; the foliar gaps overlap, so that there is technically a dictyo- 
stelic state, but, as Professor Gwynne-Vaughan remarked, it is not far 
removed from solenostely, and it corresponds in fact to that seen in Anemia. 
The leaf-trace itself consists of a single strap-shaped strand, which again 
is a primitive feature, though shared by some Ferns which have progressed 
to higher differentiation ; it is characteristic especially of the Simplices and 
Gradatae, and among them it is a feature of those types which are regarded 
as being anatomically the more primitive. In actual detail of structure 
the leaf-trace of Plagiogyria corresponds very closely with that of Anemia 
(compare Prantl’s Figs. 30, 32, Taf. Ill of his ‘ Schizaeaceen ’), while the 
whole vascular system of the axis corresponds also in its main features to that 
shown by him for the same genus (compare Prantl’s Fig. 27, a , l\ Taf. Ill, 
1 . c.); there is, however, in Anemia only a single central protoxylem-group 
in the leaf-trace, while in Plagiogyria there are two or sometimes more ; 
but, as has been seen, there is only one at the extreme base, so that the 
correspondence with Anemia is the closest at this point, where the leaf-trace 
originates (compare Boodle, ‘ Ann. of Bot./ vol. xv, p. 382). The mesoxylic 
origin of the protoxylem of the leaf is a character shared with many Ferns ; 
its quick fading out as it enters the axial system is matched by what is 
seen in Anemia (Boodle, 1 . c., p. 384). The general character of the vascular 
