HISTORY OP BRITISH PERNS.
each pinna having the margin divided by four or five deep,
sharp teeth, the rest of the pinnules and lobes having from
one to three similar teeth. The main rachis of the frond,
as well as the partial rachis of each pinna, have a narrow
winged margin, that is to say, a very narrow leafy expansion
along their sides, throughout their length; and this is perhaps
the most obvious technical point, except size, by which
to distinguish the present plant from A. lanceolatum. In
structural details they very much resemble each other, so
that in description they appear very similar, although to the
eye they are at aU times distinct.
The fronds being rigid and opake, the venation is less
evident than is usual in Eerns. It consists, in each pinnnle,
of a central or principal vein, which throws off a venule
towards each lobe or serrature, and in the larger pinnules
some of these venules become divided, so that a veinlet is
directed towards each of the serratures into which the margin
is divided. On two or more of these veins a sorus is
produced, which in form is short compared with those produced
by most of the genus; the actual form is oblong,
rather flat on the side by which they are attached; and they
are covered by an indusium of similar form, which is waved
and indented on the free margin. Sometimes the sori keep
quite distinct, but it is not uncommon for them to become
confluent so as to cover nearly all the under-surface of the
whole of the little pinnules.
There are some who doubt this species being really a
native of Britain, on the ground that it is not now to be
found in the places where it is said to have been originally
met with. We have been favoured by Mr. Shepherd, of
Liverpool, for many years a cultivator of Eerns, with a frond
gathered at Matlock, in Derbyshire. It has, moreover, been
met with on a very old wall at Tooting, and also on rocks
near Stonehaven; and considering that it is a very small
plant, and that the places where it would be most likely
to occur are generally the most inaccessible, and, therefore,
the least likely to be searched — considering, moreover,
the many probable localities which exist, and have not
been carefully explored by any keen botanical eye, we
think the probability is that it is really indigenous, though
from these causes it is overlooked. While so many probabilities
exist in favour of its being native, we are not
justified in rejecting the statements which the older botanists
have left us.
This species is too rare to be often trusted on rock-work,
unless where every provision, such as shade, shelter, and
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