164 HISTORY OF BRITISH FERNS. 



tliirds the height of the fertile ones, assume a spreading or 

 horizontal position, and are attached to the caudex by a 

 very short scaly stipes. The fertile ones, which are situated 

 in the centre of the tufts, are erect, from one to two feet 

 high, the stipes, which is sparingly furnished with long 

 pointed scales, being nearly half the length, and of a dark- 

 brown colour. 



The veins are not very evident in the fertile fronds, on 

 account of the contraction of the parts, but they resemble 

 those of the barren ones, except in having a longitudinal 

 venule on each side the midvein, forming the receptacle 

 to which the spore-cases are attached. The midvein is 

 prominent, and produces a series of veins on each side, 

 these becoming forked, and extending almost to the margin, 

 terminating in a club-shaped head. In the fertile fronds 

 the veinlets are necessarily shorter, and connected, as 

 already mentioned, by the longitudinal venules which 

 bear the fructification. The spore-cases are thus arranged 

 in two linear sori, one on each side the midvein ; 

 these are distinct while young, but often become con- 

 fluent, covering the whole under-surface of the pinnse. 

 The indusia, by which they are first covered, when 

 mature, burst along that side towards the midrib, and 



