THE BLACK MAIDENHAIR SPLEEN WORT. 83 
both these forms, though on a small scale, are shown in our Plate. 
The ovate attenuated form might be supposed to indicate a. less 
mature condition of the plant, but this explanation we are scarcely 
prepared to adopt; for fronds equally small occur in which the 
pentangular outline is preserved, while again the ovate fronds are 
often abundantly fertile; it is perhaps rather an instance of that 
profusion of form, in Nature, which mocks at our specific definitions. 
The larger of the pentangular fronds are almost quadripinnate. The 
pinne, especially the lowest pair, which are opposite, and are also the 
largest, are nearly of the same outline as the frond itself, of which 
they are miniatures, excepting that as the pinnules are alternate and 
not opposite as the lower pair of pinnœ are, there is a degree of 
obliquity at their base which almost produces a trapeziform outline ; 
their apices, as well as that of the frond, and generally those of the 
pinnules also, are caudate, with a few sharp deep distant teeth. The 
larger pinnules of the lowest pinne are somewhat obliquely ovate 
with a long attenuated point, and their divisions, the secondary 
pinnules, are lanceolate, deeply pinnatifid at a very acute angle into 
linear erect lobes, the lower of which are about three-toothed, while 
those above them are bifid at their points, and those at the apex 
form simple teeth, which as well as the teeth of the lobes are narrow 
erect and acute. The pinne towards the apex of the frond, and the 
pinnules towards the apices of the pinnee, become gradually narrower 
and less compound than these basal ones, until they are both 
reduced to linear-lanceolate sharply-toothed lobes, which latter gra- 
dually merge into the simple linear teeth of the caudate extremities. 
A similar mode of division, but on a smaller scale, obtains in the 
smaller forms, the fronds being only tripinnate, and the secondary 
pinnules narrower, and less deeply lobed. The veins, though slender, 
are very distinct; they consist of a series of furcations, that is to 
say, the vein which represents the midvein of the pinnules forks 
below each of the lobes or teeth, and the venule thus produced pro- 
ceeds along the tooth or lobe until it nearly reaches the apex, being 
where the margin is toothed simple, and where it is lobed again 
forked once or twice according as there may be two or three apical 
teeth. The sori are very narrow, linear, borne as in Adiantum- 
nigrum contiguous to each other, and near the centre of the pinnules. 
G 2 

