114 HISTORY OF BRITISH FERNS. 



beyond the margin of the fronds, this vein or receptacle 

 being enclosed within an urn-shaped involucre, consisting 

 of two nearly orbicular compressed valves, which are spi- 

 nosely serrate on the upper margin. 



It is a species widely distributed throughout the United 

 Kingdom, and is found in many other parts of the world. 

 It requires the same conditions for its successful cultiva- 

 tion as does the Trichomanes, to which genus the reader is 

 referred. ; ... 



It is the TricJwmanes turibndgense of Linnaeus. 



HYMENOPHYLLUM IJNILATERALE, Willdenow. Wilson's 

 Filmy Fern. (Plate XV. fig. 3.) 



This plant is by English botanists most commonly called 

 Hymenopkyllum Wilsoni, but there is no ground to doubt 

 that it is identical with H. imilaterale, a name published 

 by Willdenow long before that of Wilsoni ; we have, there- 

 fore, adopted Willdenow' s name on the ground of priority. 

 The species is a small moss-like plant, with numerous 

 creeping filiform stems, generally growing in dense tufts, 

 and producing a crowded mass of semi- drooping, brown- 

 green, half -transparent fronds, averaging three or four 

 inches in height. The fronds are of a linear-lanceolate 

 form, and pinnate ; the rachis is usually somewhat curved, 



