














166 THE BRITISH FERNS. 
fronds, less elongated and slighter in the barren ; smooth, rounded 
behind, channelled in front, the base ebony-coloured, pale green 
upwards; lateral, and adherent to the caudex. Rachis also smooth 
and channelled in front, the secondary rachides bearing a few small 
scattered scales, and loose spreading deciduous hairs; similar hairs 
also appear here and there on the veins beneath, and along the 
margins of the lobes. 
Fronds from six or eight inches to four feet in height, including 
the stipes, and from about four to ten inches in breadth, lanceolate 
or oblong-lanceolate, scarcely narrowed below, delicate green, 
membranaceous, erect, pinnate; the barren ones having appa- 
rently broader leafy segments, while those of the fertile fronds 
seem to be narrower and more acute, owing to the rolling in of 
the margin over or towards the sori. Pinne numerous, sub- 
opposite or alternate, spreading, linear-lanceolate, deeply pinnatifid. 
Segments oblong, obtuse or sometimes acute, straight or falcate, 
entire or slightly sinuate-lobed; the basal ones, especially those on 
the anterior side, often longer than, and quite distinct from, the 
rest. The fertile fronds differ from the sterile ones in having the 
margins of their segments revolute, and in being taller, with 
stouter stipites. 
Venation of the lobes consisting of a stout costa or midvein, 
flexuous in the upper part, from which proceed alternate once or 
twice forked veins, the venules running out to the margin. The 
veins become forked very soon after leaving the midvein. 
Fructification on the back of the frond, occupying the whole 
under surface in the fertile fronds. Sori small, round, situated 
near the base of the venules, i. e., just above the fork of the vein, 
and forming a line on each side the midvein, and about equally 
distant from it and the margin, though apparently marginal from 
the involution of the edge of the frond; they are at first distinct, 
but often become laterally confluent, and sometimes effused over 
the whole of the small space between the rolled-up margins. 
Indusium a small delicate roundish-reniform membrane, attached 
by its posterior edge, the free margin lacerate and glandular. 
Spore-cases numerous, brown, obovate. Spores oblong or reniform, 
strongly muricated. 

