TEICHOMANES. 175 



from which in the native species it is easily distinguishable, 

 although in some exotic kinds the differences almost vanish. 

 The sure technical mark by which to distinguish Trichomanes 

 and Hymenophyttum among the British Ferns, lies in the 

 fact of their spore-cases being contained within deep urn- 

 shaped pits or recesses at the margin : in these two families 

 the fructification is at the margin instead of being situated 

 at the back of the fronds. Trichomanes is known from Ey- 

 menopJiyllum by its urns, or involucres as they are called, 

 being entire, while those of Hymenophyllum are split length- 

 wise into two valves. In both cases the spore-cases are 

 clustered around hair-like receptacles, which are, in fact, 

 the ends of the veins of the fronds projecting into the urns. 

 In Hymenophyllum these hairs are always shorter than the 

 urn, but in Trichomanes it is usual for them to project more 

 or less, so that the fronds become somewhat bristly when 

 very full of fructification ; and hence has arisen the com- 

 mon 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 receptacles. 



TEICHOMANES RADICALS, Swartz. The Bristle Fern. 

 (Plate XVIII. fig. 1.) 



