94 HISTORY OF BRITISH FERNS. 



a broad-angled base, tbe lines of wliicb usually exceed 

 a right angle, and they are attached to the rachis of the 

 pinnae by a short, distinct, slender stalk, which does not 

 form a line with either margin. The pinnules have 

 branched free veins ; and the sori are generally ranged 

 in a row on each side the midrib, and are covered by a 

 peltate scale or indusium. 



The highly-developed form of the species alluded to as 

 having its basal pinnules deeply lobed, is the variety 

 sub-tripinnatum. It is not uncommon, and does not 

 differ materially in any other particular but that of the 

 division of the pinnules ; being, however, rather more lax 

 than the usual forms, it is one of the most elegant of them 

 all. The variety decompositum is a form still more divided 

 in the same way. 



The variety proliferum is another very elegant and 

 highly-developed form. This has the pinnules narrowed 

 and attenuated, more or less lobed ; and the stipes and 

 rachis bear freely little buds or bulbils, which become 

 young plants. It has been found in Devonshire. 



The variety imbricatum is a very remarkable form, 

 differing from the type in the very narrow linear-lanceolate 

 outline of the frond, as well as in having the pinnules, 



