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 

 '' indusium thrown back ; the inferior indusium 

 is entirely removed, and the attachments of the 

 thecae are indicated along the margin of the 

 shaded part ; on the right the unshaded part 

 -^ represents both the indusia thrown back, to- 

 jjjjj | gether with the thecae contained between them, 

 -yj2 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. 



