142 
BRITISH FERNS. 
16 . Mephr odium rigidum. Rigid Riicklesvfern. 
Caudex short, stout, erect. Stems scaly, nearly as long as 
the leafy part of the frond. Frond from 8 to 12 inches long, 
oblong, pointed, erect, rigid, glandular. Pinnae horizontal, 
broad, and tapering. Leaflets sessile, oblong, serrated. Veins 
forked. Sori in two rows. Involucres kidney-shaped, glandular, 
and fringed. 
The fronds of the Rigid Buckler-fern rise in a tuft 
from the apex of the caudex, they are of a fresh green 
colour, and have a pleasing 
scent, owing to the presence 
of balsamic glands. The pinnae 
are near together on the upper 
part of the frond, but more 
distant below. The frond al- 
ways tapers to the summit, 
but it decreases very little be- 
low the shoulder, indeed there 
is one form of the Rigid 
Buckler-fern where the lowest 
pinnae are the largest, giving 
a triangular form to the frond ; 
but, as a rule, there is a slight 
decrease of width towards the base. The stem occupies 
nearly half the length of the frond. The leaflets cloth- 
ing the pinnae are narrow, oblong, and serrated. The 
sori are crowded, very abundant, and often becoming 
confluent. They are only placed on the upper part of 
the frond. 
This fern is found only on a limestone soil. We have 
seen splendid plants brought from Ingleborough, where 
it grows freely, nestling in deep fissures in the rocks, 
always at a high elevation, and sometimes so much ex- 
