190 
ASPIDIACE^. 
variation ; it is elongate, lance-shaped, regularly pinnate ; pin- 
nae acute at the apex, and gradually diminishing from about two- 
thirds of its length to the very base, the lower pinnae being 
remarkably short and nearly triangular in their form : this at- 
tenuation of the frond towards the base is an excellent diag- 
nostic (see the left hand figure, page 187), and is alone sufficient 
to distinguish the present from any other British fern. There 
is but a very small portion of stem below the pinnae, and this is 
nearly hidden by pale brown scales. The pinnae are linear and 
acute at the apex, rather distant, deeply pinnatifid, and attached 
to the main stem only by their midrib. A separate pinna is re- 
presented of the natural size at page 187. The pinnules are 
rounded and slightly crenate ; over the entire under surface are 
scattered small, yellowish, glandular globules, which are adhesive 
to the touch, and emit a powerful but not very agreeable odour : 
it is probably in consequence of this property that the species 
has been so commonly supposed to be the Polypodium fragrans 
of Linneus. 
The veins in the pinnules of Oreopteris are alternate, and are 
either simple or branched ; in the latter case both veins are 
fruitful, as in L. Thelypteris : sometimes the veins or branches 
are again divided just before their termination, and then each of 
the subdivisions is usually fruitful ; all the veins and branches 
cease just before the margin of the pinnule : 
the clusters of capsules are circular, and are 
placed very near the extremity of each vein, 
so as to form a nearly marginal series. In 
some instances, but by no means generally, 
a small, torn, white involucre is to be seen 
near the centre of each cluster of capsules, 
as represented in the margin. This involucre 
is said to be reniform, a character I have 
never been able to detect : in general the 
masses are perfectly naked, even before the frond has unrolled, 
and the plant presents every appearance of being a true Poly- 
podium. 
