SPLEENWORTS > 649 
hundred and eighty species of Ferns, usually with a short tufted root- 
stock, and fronds of very various forms. The generic character is found 
in the sori, which are long and narrow, oblique, and distant from 
the midrib—except in those cases where (as in Lady Fern) the frond is 
much divided. The involucre is long and narrow, attached to the vein 
by one side, and opening towards the midrib. The species are natives 
of all Regions except the very cold; ten species are British. 
This genus is so large, and the species assume so great 
a variety of forms, that, unless studied botanically, it 
presents many difficulties. As we have already hinted, the key to the © 
classification of Ferns lies in those little brown patches of spore-cases on 
the back of the frond; but even these have to be regarded carefully, as 
will be experienced by the student of Aspleniums. To those who 
place reliance on superficial resemblances, it is certainly a puzzle to find 
Asplenium nidus, with Hart’s-tongue-like fronds, A.trichomanes, A. mar- 
inum, and A. filix-femina, associated in one genus. In the not remote 
past these differing forms have been separated in different genera, and 
even now certain species are so separated by some of our systematists. 
The name Asplenium is a very old one, for Dioscorides applied it to our 
Rusty-back, A. Ceterach. Several species—as, for instance, A. bulbiferum 
—produce a number of young plants upon their fronds; and when these, 
in the usual course, wither and fall to earth, the young plants readily 
root themselves. Several of the exotic species have been in cultivation 
here for a considerable period. A. rhizophyllum having been introduced 
from North America in 1680; A. Hemionitis and A. ebeneum, in 1779 ; 
A, monanthemum, in 1790; and A. fragrans, in 1793. 
ASPLENIUM ALATUM (winged). Stipes 4 to 6 inches 
high, the upper part winged, and the wings continued 
along the rachis. Fronds 1 to 14 foot long, 3 to 4 inches across, pinnate. 
The pinne bluntish, of nearly equal width (4 inch) throughout. Sori 
distant, not reaching margin or midrib. Tropical American species, 
requiring stove treatment. 
A. CETERACH (Arabian name). Scale Fern, or Rusty-back. Stipes 
densely tufted, 1 to 3 inches long, scaly. Fronds 4 to 8 inches long, 
pinnately lobed, leathery, the back densely clothed with toothed, rusty 
scales. Sori hidden beneath the scales, with scarcely any involucre. 
Native, chiefly in Western Counties. Hardy. 
A. CULTRIFOLIUM (ploughshare-shaped leaves). Stipes 4 to 6 inches. 
Fronds 6 to 12 inches long, 4 to 6 inches across, twice pinnate, oval- 
triangular; pinne 3 to 4 inches long, broadly toothed or lobed. Sori 
clear of edge and midrib. Introduced from the West Indies, 1820. Stove. 
IV.— 39 
History. 
Principal Species. 
