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THE FERN WORLD 
the vegetable substances which slowly accumulate in the 
tiniest crevices. Yet, though this is from its very nature 
a rock-loving Fern, and mostly found on rocks, it attains 
its finest proportions when growing on the moist and shel- 
tered side of a liedge-bauk. In such a position its fronds 
may attain a length of as much as eighteen inches, though 
its ordinary length is less than six inches, and, under some 
circumstances, it never exceeds a length of two or three 
inches. 
Description. — The general resemblance between the 
present species and Asjjlenium viride has already been 
referred to. In both, rootstock and fibrous rootlets are 
similar. But Trichomanes being a much more robust and 
abundant, as well as a larger species, produces a greater 
abundance of rootlets, which are often of great length, and 
penetrate a considerable way through the crevices of the 
rocks, or the joints of the masonry on which the plant is 
growing. The principal mark of distinction, however, 
consists in the colour of the stipes and racliis, which in the 
present species are both of a dark-purple throughout their 
entire length. The pinnae in Trichomanes are less round than 
in Viride, being more oblong or egg-shaped, and their margins, 
instead of being cleft, or serrated, are usually entire. 
They are generally set on in opposite pairs, though some- 
times towards the upper side of the frond in alternation ; 
and so closely are they arranged on the racliis, that 
adjoining pairs sometimes overlap each other. In colour 
they are dark-green, largest about the centre of the frond, 
and gradually diminishing in size towards the base and towards 
the apex. The stipes is extremely short and brittle. The 
pinnae are attached to the racliis by very narrow points, 
which are in reality the continuation of their mid-stems. 
There is, however, no distinct stalk. The venation consists 
of forked venules, which branch from the central mid-vein 
