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HISTORY OF BRITISH FERNS. 
cient by which to recognize it, among the very limited 
number of kinds which are found in a wild state in Britain, 
is not its proper distinctive mark. The real characteristics 
lie in the veins and in the sori. The former may be readily 
seen by holding a pinnule between the eye and a strong 
light, and the latter by lifting up the little reflexed lobes 
which occur here and there at the margin on the under- 
surface. The veins are dichotomously forked, that is, 
separating into two equal branches, beginning from the 
base upwards, the forking being several times repeated, 
producing close parallel radiating venules which extend 
to the margin. The sori are produced on the reflexed (or 
bent-under) membranous expansions of the margin of the 
fronds, which form the indusia, these indusia being tra- 
versed by veins which bear the sori. There is only one 
native species which possesses these characteristics, and 
this is certainly one of the most beautiful, as it is also one 
of the rarer of our indigenous Ferns ; and being of small 
size and of evergreen habit, it is one of the most desirable 
of all for culture in a Wardian case. 
The name of the genus comes from the Greek adiantos, 
which signifies dry, or unmoistened ; and is applicable to 
these plants, from their possessing in a remarkable degree 
