r
plants may be distinguished i’rom each other, I must add that I
consider the extreme difference between dentata and angustata is
lost sight of when an intermediate series, running through the
original fragile, is carefully examined; and further, that regia no
where exists iu a native habitat in this country, and is not therefore
to he considered as connected with the inquiry : having said
this, I shall make no attempt to enforce my opinions, but leave
the judicious botanist to form liis own.
The lateral veins are alternate, and each is usually divided
into three or fom- branches, one extending to every serrature in
each lobe of the pinnula. The lower detached figure iu page 33
represents a pinnula, showing the veins and points of the attachment
of the thecæ ; the figm-e immediately above it represents
a lobe of the same pinnula ; almost every vein hears a mass of
thecæ near its extremity, the mass is circular, and is covered
by a loose white membranous indusium, which is attached on
one side only, beneath the thecæ ; its margin, at the farthest
extremity from its attachment, is striated, and becomes split into
capillary segments, or sometimes torn in a ragged manner, and
at length entirely disappears ; the masses of thecæ rapidly
increase in size, at last becoming confluent (see page 32), where
the apex of a frond with confluent masses is represented to the
left of the cut. In cultivation I have observed that sometimes
from the plant receiving a check from exposure or improper
treatment, the masses remain of small size, and covered with the
indusium, even after the frond has withered.
This fern, in the wild parts of Scotland, Wales, and
Ireland, is particularly fond of bridges, where it establishes
itself in the interstices of the stones.
Æf f l
COMMON PRICKLY FERN .
P o l y s t i c h u m a c u l e a t u m .—Roth, De Candolle, Schott.
Polypodium aculeatum.—Linneus, Hudson, Lightfoot, Bolton.
Aspidium aculeatum, angulare, and lobatum.—Smith, Hooker.
E n g la n d .
Wa l e s .
Scotland.
I r e l a n d . ‘
L O C A L IT IE S .
Universally distributed.
T h e genus Polystichum contains the most Protean of all our
ferns. In the Magazine of Natural History, (New Series, vol. ii.
p. 48,) I have endeavoured to prove that we possess hut a single
species of this genus ; and the introduction of a second, in this
monograph, although accompanied by an expressed doubt, will
show that the views I then entertained have been somewhat modified,
if not abandoned, by subsequent observation. This genus
was established by Roth, and has been adopted by De Candolle
and Schott ; it contains but few species, and these are mostly
inhabitants of temperate climates.
Polystichum aculeatum, the Polypodium aculeatum of Lin-
neus, may he considered one of our commonest ferns. I have
seen it more or less abundantly in every county I have visited,
whether in England, Wales, Scotland, or Ireland. I t seems to
delight in the protection of man, its favourite habitat being our
hedgerows, and its luxuriance is greatly increased by cultivation,
or even by its vicinity to cultivated lands ; its occurrence on our
moors, commons, and mountains is comparatively rare, its
stature diminutive, and its appearance often unhealthy.
The roots of Polystichum aculeatum axe unusually long,
strong, and tough ; its rhizoma thick, tufted, and extremely
chaffy. The young fronds make their appearance in April and
May, the apex being circinate, bent backwards, and remarkably
graceful in its appearance : the pinnæ of the young frond are
also circinate (see the vignette at p. 42.) The fronds attain their