SECT.vm. BRISTLE FERN. 361 



urn-shaped cup or a two-valved indusium, projecting 

 from the edge of the frond. They are chiefly inhabitants 

 of the moist tropical forests, or extra-tropical regions of 

 damp and mild temperature. Great Britain only owns 

 one species of the genus Trichomanes, and two of the 

 genus Hymenophyllum, while species of these two genera 

 constitute one-fifth of the fern vegetation of our anti- 

 pode islands of New Zealand. It is more than doubtful 

 even that the Trichomanes radicans, or Bristle fern, is 

 indigenous, as it is found in no other part of Great 

 Britain except the Irish counties of Cork and Kerry, 

 growing on dripping rocks and waterfalls, or depending 

 from the walls and roofs of caverns ; and as it is also 

 found in the West Indies and the North Atlantic islands 

 its transit may be accounted for, as in other cases. 



The fronds of the Bristle fern, Trichomanes radicans, 

 are somewhat deltoid, or of a more elongated form, flimsy, 

 and beautifully reticulated when viewed with a micro- 

 scope. They rise at intervals from a creeping rhizome, 

 bristly, with narrow articulate scales, which often covers 

 the most precipitous rocks on which it grows with a 

 dark-coloured network. The rachis is branched and 

 rebranched three or four times, and the whole being 

 distinctly winged on both sides in the ^ 

 plane of the frond, the successive branches *3S&B 

 and branchlets running through the leafy &3SlSfflg* 

 part become the veins of those parts, so 

 that a segment of the frond is merely a QyPil % 

 winged vein, the wings on the branches 

 being however broader than those on the -J^ 



rachis. The veins, which divide alternately, J^^^ 

 are hard, woody, and wire-like, and, when 

 barren, terminate before reaching the Fig. 68. Trichomanes 

 ends of the segments ; but, when fertile, 

 they extend beyond the segment, the tissue of which 

 separates and distends in the form of a more or less 



