18 



BRITISH FERNS. 



The fronds rise in May, and disappear with the earliest frosts 

 of winter ; they are fertile and barren. The fertile frond is 

 nearly triangular ; like that of Adiantum Capillus -Veneris, it is 

 composed of a number of separate pinnulae, each on a distinct 

 , /? foot-stalk : the pinnae, as well as the 

 pinnulae, are alternate. The charac- 

 ter of the barren frond is very vari- 

 ous ; its appearance is very crowded 

 and crisped, like the leaves of parsley, 

 but its divisions are intrinsically the 

 same as those of the fertile frond ; in 

 both the rachis is slender, smooth, 

 pale green, and naked for rather 

 more than half its length ; the colour 

 of the frond is of a bright and beauti- 

 ful green. The upper frond, repre- 

 sented opposite, is fertile, the other 

 three are barren, and very various in 

 the character of their divisions: a 

 barren pinnula with its veins is shown 

 at the bottom (fig. e). A fertile pin- 

 nula is represented at fig a, the mar- 

 gins being rolled over, attenuated, and 

 somewhat bleached, and covering the 

 thecae, as in a state of nature : at 

 fig. b, one margin is unrolled, show- 

 ing the masses of thecae on that side, 

 together with their veins : at fig. 0, both 

 margins are unrolled, and the masses 

 d of thecae, which are perfectly with- 

 out indusium, shown in their natural 

 position. The lateral veins are al- 

 ternate, they are generally forked, 

 and a mass of thecae is attached at 

 each extremity ; the veins do not 

 reach the margin; this is shown at 

 fig. d. Each of the pinnulae is some- 

 what auricled near the foot-stalk, on 

 one side only. (See a, b, c, d,) The 

 masses are composed of very few 

 thecae, which renders their form in 



