81 BRITISH FERNS. 



often abundantly produced, so as to become crowded on tha 

 pinnae. 



The two species of Woodsia are found only in high moun- 

 tain regions, where they grow from the crevices of the mois- 

 tened rocks. They are both rare, though, from the inacces- 

 sible localities in which they only occur, they may really be 

 more abundant than is generally supposed. 



CHAPTER XVIIL 



THE BRISTLE FERN. 



THE Trichomanes, or Bristle Fern, is one of the most rare among 

 our native Ferns ; the one indigenous species being among 

 the few which are very seldom met with, and that within a 

 very narrow range. Unlike in texture all the other native 

 kinds excepting the Hymenophyllums, being quite pellucid, 

 and of the most delicately crisped appearance imaginable, 

 it may be distinguished from them by this mark alone. The 

 fructification, too, is here totally unlike that of all others, 

 except the Hymeno2)hyllums. The technical mark distin- 

 guishing Trichomanes and Hymenophyllum from the other 

 British Ferns, is found in their spore-cases being contained 

 within deep urn-shaped pits or recesses at the margin ; the 

 fructification therefore being at the margin instead of at the 

 back of the fronds. Trichomanes is known from Hymeno- 

 phyllum by its urns, or involucres as they are called, being 

 entire, while those of Hymenophyllum are split lengthwise 

 into two valves. In both, the spore-cases are clustered 

 around hair-like receptacles, which are the ends of the veins 

 of the fronds projecting into the urns. In Trichomanes it is 

 usual for these receptacles to project more or less, so that 

 the fronds become somewhat bristly when very full of fruc- 

 tification j and hence has arisen the common name of Bristle 

 Fern, which is applied to the group. 



The name Trichomanes itself has the same signification : 

 it comes from two Greek words, meaning hair, and excess, in 

 reference to these projecting hair-like bodies. 



EUROPEAN BRISTLE FERN. [Plate X. fig. 1.] 



This Fern, like many others, has had many names. Tricho- 

 manes radicans is here adopted ; but more or less in use will 

 be found Trichomanes speciosum and Trichomanes brevisetum. 



