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HISTORY OF BRITISH FERNS. 
nearly opposite, and having more or less of obliquity, from 
the larger development of the lower side. The pinnm are 
pinnate, and the pinnules near their base often so deeply 
divided as to be again almost pinnate ; the rest are pin- 
natifid, or in the upper parts merely deeply- toothed, but 
the margins, whether deeply or shallowly-lobed, are set 
with teeth which end in short spinous points. The vein- 
ing is very similar to the more compound parts of the 
allied species. The fructification is produced in great 
abundance, the sori being ranged in two lines crosswise 
the pinnae on the larger lobes, or lengthwise on the less 
divided parts. The sori are covered by kidney-shaped 
scales or indusia, which are fringed around the margin 
with projecting glandular bodies. 
There is met with a variety or form of this Fern, which 
has the fronds shorter, almost triangular in outline, and 
often remarkably convex ; it has, moreover, usually a 
dark green colour, often with a brownish tinge. It is 
found in more exposed places than the normal form, and 
is not uncommon. 
Another variety, sometimes called nana, seems chiefly 
remarkable for its small size, seldom exceeding six or eight 
inches in height, which peculiarity it maintains under cul- 
