investing membrane or cover to the spore-cases, and its
form, origin, and mode of bursting when present. TMs, in
fact, brings us to the basis of the classification wliich has
prevailed till witldn comparatively very few years, and even,
to some extent, to the present time.
Another feature has, however, latterly been adopted by
many botanists skilled in the knowledge of Eerns, as forming
the leading characteristic of their family relationsMp, the
groups thus brought together representing the modern classification
of Eerns. The feature thus adopted, as affording
the marks of family recognition, is the veining of the fronds ;
and probably, as at present employed, in conjunction with the
characters derived from the clusters of spore-cases and their
covers, there is but little scope for further improvement.
The tendency of the system is, however, towards subdivision
of the family groups, and in this direction it is perhaps
somewhat liable to err. We shall introduce a summary of
the groups and species adapted to Mr. John Smith’s plan of
arrangement, in accordance with the venation ; the picture
presented by onr few native species must not, however, be
taken as a proper representation of this system of classification.
In the more detailed descriptions it will be more convenient
if we foUow an alphabetical order.
A TABLE OE THE GROUPS AND GENERA OP THE BRITISH
EERNS AND ALLIED PLANTS.
1. m m s —F i L i c m
Elowerless plants, bearing seed-vessels (spore-cases) on
the backs or margins of their leaves (fronds). The
British Eerns belong to groups which are called
PolypodiacecR, OsmundacecR, and Opidoglossacece.
i. P olypodiacetB = Eerns having the leaves rolled u p in a
circinate or crozier-hke manner while young, and the
spore-cases girt with an elastic ring, and bursting in
an irregular manner. It comprises the lesser groups
of Bolypodiea, Aspidiece, Aspleniece, Pteridem, and
BicJcsoniem.
A. P o ly p o d i e jE = Eerns whose clusters of spore-cases
have no special membranous cover (indusium). It
contains the genera Polypodium and Allosorus.
1. Polypodium— ~Doxsú-ir\ñÍGá. Eerns, with the sori
exposed.