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HISTORY OF BRITISH FERNS. 
affinity. The affinity of the Lady Fern is properly with 
the Aspleniums, and there is less reason to dispute the 
conclusions of those who actually place it as a species of 
Asplenium; although,, as the hippocrepiform sori indicate 
a real difference between them, and the genus Asplenium 
is rather a crowded one, it is a convenience to have them 
separated. The mark by which the Aspleniums and their 
allies are known, in addition to the elongated form of the 
sorus, is its position on the side, not the back, of the 
veins; the receptacle being lateral, as it is said. The 
Aihyrium group is known from Asplenium by having its 
indusium fringed on the free margin by capillary segments, 
and by the horseshoe-shaped basal sori; while in the 
Asplenium the margin of the indusium is without the 
membranous fringe, and the sori are not turned back 
along the reverse side of the vein. There is, as already 
mentioned, only one indigenous species of Aihyrium . The 
Asplenium fontanum is sometimes admitted, but it does 
not properly belong to this genus. 
The name is derived from the Greek, and comes from 
athyros, opened; the allusion being to the position into 
which the indusium is forced by the swelling spore-cases, 
bursting cut, as it were, like an opened door, after the 
