126 FILICES 
6. SHIELD FERN (Polijstichum). 
1. Rough Alpine Fern or Holly Fern (P. lonchitis).—Fronds rigid, 
simply pinnate ; pinnz not lobed, serrated, spinous, eared at the base. The 
plants of this genus are nearly allied to those of Lastrea, yet they are truly 
distinct, a most marked feature of difference being in the form of the indu- 
sium which covers the seed-clusters. This is circular, and not kidney-shaped, 
and is attached by a small stalk at the centre. The Polystichums, too, are 
more rigid in texture than the Lastreas, and more spinous. 
We have not many ferns growing on high mountains exposed to the 
bleak winds; yet the Holly Fern, like the plant from which it takes its 
name, thrives well on alpine heights, and, indeed, is found only in such 
situations. 
Very beautiful specimens are gathered from the Clova Mountains, where 
this evergreen plant presents a beautiful appearance as it springs out from 
the rocky crevices; and it is extensively distributed on the Scottish moun- 
tains, as well as in the north and west of Ireland. A few rocky hilly places 
in the north of England are named as its localities, as Falcon Clints, Tees- 
dale; Mazebeck Scar, Durham; and Langcliffe, near Settle; Giggleswick, 
and some other places in Yorkshire. It grows on Snowdon, on heights 
which the traveller hesitates to climb, thriving even on the loftiest summits 
of the mountain. It is, however, among the shady clefts of the broken 
masses of rock, at a less elevation, that this fern attains its greatest luxuri- 
ance. In some damp and shady spots among these acclivities it is sometimes 
a foot and a half high, though in ordinary cases the plants are not more than 
half a foot in height. The stalk of the frond is very short, and the dark 
glossy green leafy part is mostly leathery, firm, rigid, and sufficiently prickly 
to remind us of the holly, but it is occasionally thinner and less upright in 
growth. The young fronds appear early in spring, among the yet verdant 
fronds of the former year. They rise in a tuft from the extremity of a 
scaly rhizome, and their outline is narrow, linear, and tapering at the upper 
part. They are pinnate, with short, crowded, overlapping, twisted pinne, 
which are somewhat crescent-shaped ; the upper side having at the base an 
ear-shaped projection, while the lower side has the appearance of having had 
a piece cut out. The veins are twice or thrice branched, reaching nearly to 
the margin, without uniting with others. The indusium is a membrane-like 
scale, and the clusters of fructification form a continuous line on each side 
of the mid-rib, and even with it. They are often very numerous on the 
upper pinne. 
The Holly Fern is very difficult of cultivation. It is called by some 
writers Aspidium lonchitis, Aspidium being the name of the entire genus, 
but the British species belong to the section Polystichum. 
2. Common Prickly Fern (P. aculedtum).—Fronds rigid, linear, or 
lanceolate, twice pinnate ; pinnules acute, running down the stem. This is 
quite a common fern, one which is found almost throughout the kingdom on 
hedge-banks and shady places, its dark green and handsome fronds contrasting 
with the brighter tinted Hart’s-tongue Fern, or the feathery grasses beside 
it. It grows also in woods, but is seldom seen on the open heath, or alpine 
