68 HISTOUY 01’ BKITISH PERNS.
often spread and become confluent, so that almost the
entire under-surface of the frond is covered with the spore-
cases. The indusium is narrow, with its free margin entire;
this soon becomes pushed away by the growing sori, and
is lost.
This species is very variable. In dry and exposed places
it is small, and obtuse in its parts, wdrilst in sheltered,
shady places it is much drawn out or elongated. The extreme
states have been considered as varieties; and it is
true that occasionally there occur plants of which this bluntness
seems characteristic, and to these the name of obtusum
is sometimes given; while on the other hand, sometimes,
but rarely, the form in which all the parts are much narrowed
and very acute is met with, and this is called acufim.
These differences become less marked in the cultivated plants
than in those which occur in a wild state, and hence they
seem hardly to deserve to be considered as permanent
varieties. The species has also been met with having the
fronds variegated with white.
The ordinary forms of the plant are very commonly met
w'ith growing on rocks or old walls, and on hedge-banks in
a sandy soil. The latter situations, where they grow most
vigorously, are often beautifully adorned by the drooping
tufts in which they occur. The extreme forms are more
rare.
Tliis is one of the more useful evergreen Eerns for shady
rockwork, as it will grow with freedom if planted in sandy
soil, which is just kept moistened either by natural or artificial
means. As a pot plant it is easily manageable.
The blunt-leaved variety alluded to above, is believed to
be the A. obtusum, and the narrowed form the A. acutum,
of continental authors.
A splenium fontanum, R. Brown.—Tae, Smooth Eock
Spleenwort. (Plate X I I I . fig. 2.)
This is a small tufted-growing species, seldom seen more
than tliree or four inches high under ordinary circumstances ;
in a hot-house, where its parts become more lengthened, it
sometimes reaches six or eight inches high, but we never
saw this stature exceeded in cultivated plants, and it is but
rarely attained. The small fronds are evergreen, and mostly
grow nearly upright ; they are of a narrow, lanceolate form,
rather rigid in texture, of a deep green above, paler beneath,
and supported on a very short stipes, which has a few
narrow, pointed scales at the base. In division they are
bipinnate, the pinnæ being oblong-ovate, and the pinnules
obovate, tapering to the base, the superior basal pinnule of
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