73 



late; segments alternate, linear, entire or bifid, obtuse. Invo- 

 lucres solitary in the axils of the upper segments, shorter than the 

 filiform receptacle. 



Trichomanes radicans, Swartz. Hooker. Babington. Moore. New- 

 man. Trichomanes brevisetum, Brown. Smith. E. B. ed. 2, 

 1445. T. speciosum, europseum, pyxidiferum, and alatum, 

 of authors. Hymenophyllum alatum, Smith. E.B. 1417. 



The original locality of the Bristle Fern is doubtful, as speci- 

 mens collected in several parts of the world, not essentially differ- 

 ing from our own, evince a wide distribution ; though, being found 

 in the West Indies and in the islands of the North Atlantic, ren- 

 ders its transit hither consistent with those natural causes that 

 have enriched the catalogue of British vegetation with many other 

 productions of warmer climates. At present this may rank as a 

 rarity to the home botanist, not being found in any other part of 

 the United Kingdom than in the Irish counties of Cork and Kerry, 

 where it grows more or less abundantly on dripping rocks, about 

 lakes and waterfalls, and depending from the walls and roofs of 

 caverns. The rhizoma creeps and spreads like that of Polypodium 

 vulgare, and in some situations attains a length of several feet, 

 often covering the moist rocks on which it grows with a complete 

 network ; it is of a dark colour, almost black, and clothed with 

 narrow, bristle-like, articulated scales. The fronds, developed at 

 intervals as the rhizoma extends, are from three inches to a foot in 

 length, and generally pendulous, in consequence of the position 

 they occupy on the sloping or perpendicular faces of the rocks : 

 the general outline is somewhat deltoid, but in very luxuriant 

 plants it passes into an oblong-lanceolate form very much acumi- 

 nated, constituting the variety Andrewsii of Mr. Newman, Hist. 

 Brit. Ferns, 292. The rachis is winged throughout on each side, 

 corresponding with the plane of the frond, the leafy portion of 

 which seems to consist only of a continuation of these wings in a 

 broader form along each side of its branches, which latter consti- 

 tute the veins; this structure renders all the ultimate divisions 

 narrow and linear. The veins, dividing alternately, are hard, 

 woody, and wire-like, and, where barren, terminate before reaching 

 the ends of the segments ; but where fertile they extend beyond 

 the segment, the tissue of which separates and distends in the 

 form of a more or less elongated cup around the prolonged vein 

 this cup is the involucre, the prolonged vein the receptacle, referred 

 to under the generic and specific characters. The thecse form a 

 small globular cluster round the receptacle at the bottom of the 

 cup, beyond which latter organ, as they advance to maturity, the 

 modified vein extends in the form of a bristle, varying in its ex- 

 serted length from two to four or even six times that of the invo- 



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