THE BLADDER FERN. 253 
by Sir W. J. Hooker, who, however, does not separate it from the 
Davalliee, but observes that “it may assuredly be considered a 
connecting link between the Davalliaceœ and the Aspidiaceœ, har- 
monising better with the former than with the latter, especially 
with the group Leucostegia.” This group Leucostegia is, we think, 
better separated from .Davallis and combined with Acrophorus, 
under which name it forms a good genus of the Cystopteridee. 
The indusium of Cystopteris when assuming the truncated semi- 
calyciform character it sometimes bears, appears to stand in the 
same relation to the hemitelioid scale found behind the sorus in some 
species of Alsophila, as the more perfect cup-like indusium of 
Woodsia, a true cup in some exotic species, does to that of Cyathea. 
These genera thus become, to a certain extent, connecting links 
between the polypodiaceous and cyatheaceous series. 
The few species referred to Cystopteris, are widely dispersed, 
oceurring chiefly in temperate climates of both the old and new 
world, and of both hemispheres. They also extend to the arctic 
regions and to the tropics. 
The name of the genus comes from the Greek kystos a bladder, 
and pteris a fern, whence the English name Bladder Fern. 

SYNOPSIS OF THE SPECIES. 
Fronds lanceolate ; caudex short tufted. 
+ Fronds bipinnate. 
1. C. fragilis: pinnules (of the middle part of the frond) ovate acute, Ba 
or subpinnate ; teeth of the segments acute. 
var. angustata: pinnules lanceolate or lanceolate-ovate, pinnatifid or sub- 
pinnate ; teeth of the segments narrow elongated acute. 
var. dentata: pinnules oblong or oblong-ovate, distinct, pinnatifid ; teeth 
of the segments blunt. 
var. Dickieana: pinnules oblong or oblong-ovate, imbricated, lobate, with 
shallow blunt teeth ; pinne deflexed. 
+t Fronds subtripinnate ; pinne ovate. 
2. C. regia: pinnules ovate-oblong, deeply pinnatifid or pinnate ; ultimate seg- 
ments linear, with short blunt or retuse teeth. 
** Fronds deltoid or subpentangular ; caudex creeping. 
3. C. montana: fronds tripinnate. 

