86 THE BRITISH FERNS. 
deciduous scales, otherwise smooth and glabrous; lateral and adhe- 
rent to the caudex, and somewhat distant. Rachis quite smooth ; 
that of the central branch deflexed, of the lateral branches spreading. 
Fronds from four to twelve or fourteen inches in height, including 
the stipes, the leafy portion averaging from four to six inches in 
length and breadth, delicately membranaceous, bright lively green, 
quite smooth; in form deltoidly-pentangular, the pentagon being 
described by the points of the three branches and those of the two 
basal pinnules of the lower branches, which latter diverge so as to 
represent two separate angles. The fronds are ternate, that is, they 
consist of three nearly equal portions or branches, as indicated by 
the vernation. Branches pinnate or subbipinnate, differing from 
each other chiefly in this, that while the upper or central one has 
its sides nearly equal, the two lateral ones have the pinne on their 
lower side larger, sometimes twice as large as those on the upper _ 
side, so that they are obliquely triangular. Pinne opposite, variable 
in outline from ovate to linear-oblong, acute, usually pinnate at 
the base, pinnatifid above, and acute as well as nearly entire at the 
apex; those of the central branch more decidedly pinnate than 
those of the lateral ones. Pinnules or lobules oblong-obtuse, crenate 
or crenato-lobate, smaller and less divided towards the apex. 
Venation of the more compound, that is the crenato-lobate pin- 
nules, consisting of a flexuose costa or midvein with alternate veins, 
one to each lobe, these veins being pinnato-furcately branched, with 
the venules extending to the margin. The veins of the crenate pin- 
nules have fewer branches or venules. The first anterior venule 
bears a sorus some distance below its termination. 
Fructification on the back of the frond, and spread over its whole 
surface. Sori small, circular, consisting of numerous crowded spore- 
cases, quite uncovered, arranged in a linear, often crowded, series, 
along each side of the pinnules, near to but distinctly within the 
margin, the sori being seated some distance below the apex of the 
venules. Sometimes the fronds are less abundantly fructified, and 
the sori appear distant and scattered. Spore-cases small, dark- 
brown, roundish-obovate, attached by a slender pedicel. Spores 
ovate, roundish, or oblong, with a granulated surface. 
Duration. The caudex is perennial. The fronds are annual, 

