THE BRITTLE BLADDER FERN 
285 
to twelve or fourteen in height, according to circumstances 
of growth. But the root of this plant has a spreading 
habit, and frequently, when growing in congenial positions, 
spreads or multiplies into two or three tufted crowns, each 
of which sends up a cluster of fronds. The stipes, which is 
excessively brittle and herbaceous, is somewhat variable in 
length, being in some specimens shorter than the leafy 
portion, in others about the same length, and occasionally 
much longer. At its base it is of a reddish colour, but 
becomes green above, when young being frequently green 
throughout : the rachis being also sometimes green through- 
out, and sometimes tinged with red. The general shape of 
the frond is broadly lance-shaped, or narrowly ovate, tapering 
to a point at its apex, like most Ferns, by the gradual 
diminution in the length of the pinnae, broadest in the 
centre, and tapering very slightly towards its base. It 
is bi-pinnate, the pinnae being set on opposite sides of 
the rachis, sometimes in pairs, but often in irregular 
alternation. The pinnae are narrowly ovate in form, 
and are again divided into small ovate pinnules set on 
opposite sides of the mid-stems of the pinnae in irregular 
alternation. The pinnules are deeply cleft into lobes, some- 
times almost again divided, the lobes being fringed or 
serrated. The venation consists of a wavy mid- vein running 
through the pinnules, with two or three times forked 
venules running into the lobes, and bearing upon them 
under a somewhat irregular system of distribution, roundish 
clusters of spore cases furnished each with its hood- 
like, or inflated indusium, which is attached at one of its 
sides to the lobe bearing the sorus — the point of attachment 
beino- on that side of the sorus which is nearest the base of 
o 
the lobe. When the plant is not highly developed, the 
mid-stems of the pinnae become the centres of the system of 
venation, venules branching from them into the partly divided, 
