veins and of retioulatcd veins in tho primary groups of flowering
plants, and tho value assigned to them, are significant facts; and
importance may bo equally claimed for similar differences among
the Ferns. That some auxiliary character beyond that afforded by
tho sori and their covers, is required, is very commonly admitted;
for while tho complete scries of floral organs in flowering plants
offer such numerous and varied characteristics for generic combination,
tho differential characters to he drawn from the sori in
Ferns arc exceedingly limited. And what auxiliary character is
there so proper to be employed as the vascular structure of tho
plant with which the sori aro so intimately connected ? Experience,
moreover, attests th a t it may be relied on with perfect
confidence, for it is found, with a few insignificant exceptions, that
whatever condition of the venation occurs in a particular species,
th a t condition is constant to th a t species.
The vascular system, as we have already stated,* must ho regarded
as of tho highest importance in the economy of plants, even in
reference to their propagation, for cases are not at all infrequent in
which certain extraordinary means of development, namely, adventitious
buds, are formod in direct connection with it. In the Ferns
particularly, those points of the veins which normally serve as
tho receptacles to which the sporo-cases aro attached, in other cases
become viviparous, and develope gommai or buds instead of spores.
Though thus claiming systematic importance for the venation in
Ferns, and supporting its use as a source of generic character, wo
are ready to admit th a t the question is not altogether free from
anomalies, or without its difficulties ; these are, however, not greater
than occur in the application of our imperfect knowledge to the
classification of other groups of plants, where even with ah the
variety of character afforded by the flower and seed, anomalous and
dubious species are not uncommon; nor are the anomalies hero
* Proceedings o f lAnncmn Society, ii. 2 11; and Oardencrs’ Chronicle, 1853, 86.
more difficult to ovcroomo, than those presented by all other methods
which have been proposed for tho classification of the Ferns.
Wo have already recorded* some instances in which the son of
dorsiferous and other Forns wore aberrantly situated. Tho mferonoos
to be drawn from tbe examples referred to aro, we think, confirmatory
of tho importance of tho venation. I t would thonoo appoar
that tho veins aro important structures in the economy of Fern
development, since they arc capable of originating the receptacle and
spore-oases from their surface in any part—even in unusnal parts—
of the frond. This being so, sufficient importance would appear
to attach to them, to justify their being .employed for the purpose of
assisting in the definition of genera, in a family of plants where
something more than the so-oaUed fruotifioation itself is confessedly
needed to supply distinctive oliaraotors.
Mr. J. Smith has recently proposed! to classify the Ferns according
to their mode of development from tho caudex or rhizome.
Taking advantage of the apparent difference between the growth of
those Ferns which have a oaudioiform and a rhizomatous stem, he
proposes to bring tho polypodiaoeous Ferns under two groups, which
he calls Eremohrya and Desmohrya.
In tho Eremobryte “ the fronds aro developed from the sides of a
special rhizome which has its axis of growth always in advance of
the nascent frond (oxourrent) ; the fronds aro produced from nodes
more or less distant from each other, each node producing a single
frond, which after having arrived at maturity separates hy a special
articulation formod between the node and the base of tho stipes.
After the frond has fallen the node remains in tho form of a round
concave cicatrix generally more or loss elevated. The rhizome is
solid, fleshy, and brittle, varying from long and slender to moro or
less short and thick, and is always covered with scales which unless
• Ante, p. 22.
t J. Smith, Botany o f the Voyage o f II. M .S. Herald, 22G.
I IE