16 BRITISH FERNS. 



of the lobe, it is difficult to obtain a satisfactory view of these 



parts, and still more difficult to represent them by a figure. In 



the annexed cut the lobe is supposed to be flattened : on the left 



the unshaded portion represents the superior 



~-"'/^^\V '" indusium thrown back ; the inferior indusium 



v\ 



/"r 



V h S\ ' , , ^ is entirely removed, and the attachments of the 

 ^~ jv\ _ F ^^ ^ i' thecae are indicated along the margin of the 





shaded part ; on the right the unshaded part 

 .^ ^ , ,, represents both the indusia thrown back, to- 



^—S -^ "'{ 1 I gether with the thecae contained between them, 

 ':/.r^, j ^ '-L^ the thecae occasionally protruding beyond the 

 ^^^" ""^^ indusia. 



When the pinnula is barren, there is no trace of an indusium : 

 the disposition of the lateral veins is very nearly as in the fertile 

 pinnulae, but they very obviously cease at the margin, which is 

 without a channel or vein of any kind. 



This is not only the most abundant but the most useful of 

 our ferns : in Scotland, particularly in the Western Highlands, 

 I observed it used for thatching cottages; in many parts of 

 England it serves as packing for fruit and fish, and in Wales 

 it is harvested as litter for horses. In wandering among the 

 mountains of Wales I have constantly met with sleighs drawn 

 by a ragged pony, and laden with Pteris by some industrious 

 Welshwoman. 



