150 
BRITTLE BLADDER FERN. 
The Brittle Bladder Fern is of a very delicate and 
grassy appearance, the root-stems spreading, under 
favourable circumstances, into large patches of numer¬ 
ous crowns, each of which throws up a tuft of several 
fronds, from six inches to sometimes a foot in height. 
The stipes, erect, and rather more than a third of the 
length of the frond, is brittle, dark, shining, with a few 
small scales at the base. The fronds are lanceolate, 
bipinnate ; the pinnae lanceolate; the pinnules ovate- 
acute,|cut more or less deeply on the margin, the lobes 
furnished with a few pointed teeth. In some vigor¬ 
ous plants the pinnules are so very deeply cut as to 
become pinnatifid, almost pinnate, the lobes themselves 
then resembling the smaller pinnules nearer the apex 
of the pinna? and frond. The venation, from the deli¬ 
cacy of the frond, is very readily seen. In the ordi¬ 
narily-sized pinnules there is a somewhat twisty mid¬ 
vein, giving off a side branch or vein to each of the 
lobes into which the margin is cut, these veins again 
branching into two or more venules according to the 
size of the lobe, and each branch generally bearing a 
sorus at about midway of its length. The sori are 
thus generally numerous and rather irregularly placed, 
often becoming confluent and covering the whole 
under-surface; but their number, and confluence, vary¬ 
ing much, depending upon the various circumstances 
of growth. The sori are nearly circular ; the flask or 
bladder-shaped (like a hood over them) indusia be¬ 
come in age torn or split at the point into narrow seg¬ 
ments, turned back, jagged and fringe-like, the whole 
being pushed off by the ripening spores. 
