FILTCES. 103 



when exposed to the sun, not shining, very variable in its degree of 

 division and in the shape of its ultimate segments, which are some- 

 times acute, sometimes obtuse, and vary from pinnatipartite to serrate 

 or crenate, with the bases sometimes greater than a right angle, 

 at other times wedge-shaped, often more or less decurrent on the lower 

 side. From this extreme variability of shape and cutting of the 

 pinnules or segments, I have been compelled to adopt the general 

 outline of the frond as the mode of separating C. eu-fragilis into two 

 varieties, 



Var. dentata when typical has the frond not more than bipinnate, 

 sometimes scarcely even bipinnate, and both the pinnse and the 

 pinnules are blunter at the apex than in the common form. Professor 

 Babington states that the spores of var. dentata are " warted," but in 

 all the specimens named ' dentata ' I have examined they have the long 

 sharp spur-like tubercles characteristic of C. eu-fragilis. 



Milde, under var. dentata, gives an Algerian form from Blidah, 

 collected by Gr. Munby, which has verrucose spores. This I have not 

 seen, but certainly should not refer it to eu-fragilis at all, as the 

 striking difference between the spores seems to me the only tangible 

 difference between C. eu-fragilis and 0. alpina. 



C. angustata, Sm., appears rather a finely cut form of var. dentata 

 than a narrow form of var. genuina. 



Brittle Bladder-fern. 



Subspecies (?) II.— Cystopteris alpina. Desv. 



Plates 1866, 1867. 



Milde, Fil. Europ. p. 150. 



Caudex short, rather stout, dividing into several short branches or 

 crowns, clothed with the more or less approximate bases of former 

 fronds. Fronds several, close together at the apex of each branch or 

 crown of the caudex. Stipes from one- third as long as to as long as the 

 lamina, slender and very brittle, with pale linear-lanceolate scales at 

 the base, and a few hair-like deciduous ones in the upper part, but no 

 glands. Lamina perishing in autumn, oblong-lanceolate or strap- 

 shaped-lanceolate, subquadripinnate or subtripinnate or rarely bi- 

 pinnate ; lowest pair of pinnse always smaller than the succeeding 

 pair, and generally conspicuously smaller ; pinnules bipinnatifid or 

 bipinnatipartite, rarely only pinnate ; teeth of ultimate segments 

 mostly notched, with the ultimate veins running into the notches ; 

 rachis and lamina without glands. Indusium without glands, denti- 

 culate. Spores tuberculate, with sparse large blunt tubercles. 



