THE SMOOTH ROCK SPLEENWORT. 61 
elevated margin or wing throughout, the margin extending nearly to 
the base of the stipes. 
Fronds averaging four or five inches in height, but varying from 
about three to ten or twelve inches, rigid, dark green, smooth, erect 
or spreading, narrow-lanceolate, broadest above the middle, bipin- 
nate. Pinne oblong-ovate, spreading; the lower ones smaller, 
palmately three-lobed and more distant; the uppermost ones oblong, 
and more crowded. Pinnules roundish obovate, tapering to the 
base, the lower ones distinctly stalked on the narrowly-winged 
secondary rachides, the upper ones decurrent ; their margins deeply 
notched, with from two or three to five or seven coarse, angular, 
spinosely-mucronate teeth. 
Venation of the principal pinnules consisting of a flexuous costa 
or midrib, sending off alternate simple veins one of which is directed 
towards each tooth, and extends almost to its apex. 
Fructification on the back of the frond, most copious upwards, 
but extending nearly to the base. Sori small, short oblong, from 
two to four on each pinnule, attached near the base of the veins on 
their anterior side, at first distinct, but often at length becoming 
confluent and forming large shapeless masses over the centre of the 
pinnules ; indusiate. Indusium short oblong, white, usually straight, 
but sometimes a little curved behind, rounded entire and sometimes 
slightly wavy on the anterior free margin.  Spore-cases small, 
roundish. Spores angular, rough. 
Duration. The caudex is perennial. The fronds are persistent, 
the plant being evergreen, and continuing in growth the whole 
year, under favourable conditions. 
. This Fern is readily known among the British Aspleniee, by its 
bipinnate fronds, taken in conjunction with their small stature, and 
the minuteness of their parts, six inches in length for the frond, and 
half an inch for the pinne being rather above the average growth. 
Apart from this discrepancy in size, it very much resembles the 
small bipinnate states of Asplenium lanceolatum, the structure of its 
parts being nearly identical, but in the latter the lower pinne do 
not diminish in so marked a degree. 
Roth when establishing his genus Athyrium, included the present 

