464 FILICES. [CYSTOPTERIS. 



dorsal on the middle of a venule, globose ; involucre membranous, attached 

 by a broad base to the venule below the sorus, ovate, convex, acute, at 

 length reflexed. DISTRIB. Cool damp regions; species 5. ETYM. Kvens 

 and irrupts, from the bladder-like involucre. 



1. C. frag'ilis, Bernh.; rootstock tufted, frond ovate -lanceolate 1-2- 

 pinnate, pinnse deltoid-ovate. 



Bocks and walls in mountain districts, from Sussex and Kent northwards ; 

 ascending to nearly 4,000 ft. in the Highlands; frt. July- Aug. RooMock 

 densely clothed with pale brown lanceolate membranous scales. Stipes 

 2-4 in., brittle. Frond 4-8 in. ; rachis slightly winged above, larger pinnae 

 1-1 ^ in., lobes or teeth obtuse or acute. Sori 2-12 on each segment. DIS- 

 TRIB. Europe (Arctic), N. Africa, N. and W. Asia, N. America, trop. mts. 

 and S. temp, regions. 



Sub-sp. FRAG ILIS proper ; fronds broadly lanceolate, pinnae obovate or lance- 

 olate, segments incised or pinnatifid, sori distant from the margin. 



Sub-sp. DENTA'TA, Hook. (sp. ) ; fronds sub-2-pinnate, pinnae ovate-lanceolate 

 obtuse obtusely unequally toothed, sori submarginal. 



Sub-sp. DICKIEA'NA, Sim (sp. ) ; frond ovate-oblong obtuse membranous, 

 pinna? ovate obtuse subdeflexed, segments broad crowded obtuse crenate. 



2. C. monta'na, Link; rootstock creeping, frond deltoid 3-4-pinnate, 

 pinnae and pinnules spreading. 



Alpine wet rocks, alt. 3,600 ft., very rare ; Perth. Forfar, and Aberdeen ; absent 

 from Ireland ; frt. July- Aug. Rootgtock widely creeping, sparingly scaly. 

 Stipes 6-9 in., very slender. Frond 4-6 in., as broad as long, lowest pinna? 

 1-1^ in., segments cut to the rachis, deeply sharply toothed, especially 

 towards the tip. Sori small, 18-24 on the lowest pinnules. Involticre cut at 

 the edge. DISTRIB. Arctic and alpine regions of Mid. and S. Europe (excl. 

 Russia), N.E. Asia, Rocky Mts., Canada. 



11. ASPID IUM, Sw. SHIELD-FERN. 



Habit various. Sori dorsal, globose ; involucre superior, orbicular, 

 peltate. DISTRIB. All regions; species 55. ETYM. dinrls a shield, 

 from the form of the involucre. The British species belong to the section 

 Polystichum, having free veins. 



1. A. Lonchi'tis, Sw. ; frond linear-oblong pinnate. 



Clefts of Alpine rocks and amongst large stones, from N. Wales and York 

 northwards; ascends to 3,200 ft. in the Highlands; W. and N.W. of Ire- 

 land; frt. June- Aug. Rootstock densely tufted, oblique, scaly. Frond* 

 densely tufted, 6-18 in., coriaceous, bright green, glabrous except the 

 scaly short stout stipes and rachis and veins beneath. Pinncema.ny, -1 in., 

 narrow-ovate, base auricled and obliquely rhomboid, falcate, acuminate, 

 gpinulose-serrate. Sort in 2-3 rows on each side the midrib. DISTRIB. 

 Europe (Arctic), Siberia, Dahuria, W. Asia, Himalaya, N. America. 



2. A. acnlea'tum, Sw. ; frond ovate-lanceolate 2-3-pinnate. 

 Woods, shaded hedgebanks, &c. from Skye and Ross southwards ; ascending 

 to nearly 2,500 ft. in Yorkshire ; frt. July-Aug. Rootstock short, stout, 

 and stipes and rachis densely clothed with ferruginous scales. Frond 

 6-12 in., scaly beneath ; lower pinme 4-6 in., close-set, lanceolate ; pinnules 

 obliquely rhomboid-ovate auricled, teeth mucronate or awned. Sori 1- 



