29 . 
THE RIGID BUCKLER FERN. 
Lastrea rigida. 
Plate 10, Fig. 1, Page 325. 
Amongst the most rare of the British Buckler Ferns, Lastrea 
rigida is also the only rock-growing species of the genus in 
Britain. It derives its name of rigida from its rigid and erect 
habit of growth. It has a great preference for limestone 
rocks, in the moist crevices of which it is mostly found 
growing at elevations above the sea level of from twelve 
hundred to sixteen hundred feet. Though found in only a 
few localities, it is very abundant in some places, its fronds 
being cropped by sheep, which appear to appreciate and to 
relish their flavour. 
Description. — The rootstock of Lastrea rigida is com- 
paratively thick, and it has an abundance of fibrous rootlets. 
The stipes, which is usually about half the length of the 
entire frond, being about equal in length to the leafy portion, 
is densely scaly at its base, the scales being of a reddish- 
brown colour. The entire length of the frond — leafy portion 
and stipes — is from one to two feet, its colour being a some- 
what dull green. It is bi-pinnate, lance-sliaped, or ovate, 
and sometimes triangular in shape, with triangular pinnae set 
on the rachis, which is mostly scaly throughout, in pairs 
either evenly or irregularly on each side of it. The pinnae 
are divided into oblong pinnules, which, though not stalked, 
are attached by a narrow point of their base to the mid- 
