A S P I D I U M irriguum.
Brook Shield-fern.
CRYPTOGAMIA Filices.
G en. Char. Fructifications scattered, in roundish
dots, not marginal. Involucrum umbilicated,
bursting almost all round.
Spec. Ch ar. Frond lanceolate; pinnate; leaflets deeply
pinnatifid, cut and sharply toothed. Stalk quadrangular.
Involucrum lateral, short, jagged.
D i s c o v e r e d by T. F. Forster, Esq., about the watery
margins of clear springs near Tunbridge wells. Our figure
was taken in June, 1810, from a living plant in his garden,
not at all changed by cultivation.
W e can find no described fern, nor any exotic or British
specimen, that accords with this. It agrees in some points
with A . Thelypteris, (Polypodium Thelypleris, t. 1018,) but
is much smaller, more tender and delicate, neither has it a
creeping root. The main rib is exactly square, and of a delicate
transparent green when living, pale brown when dried.
Leaflets numerous, alternate, very deeply and copiously pinnatifid,
their segments ovate-oblong, sharply cut and toothed,
merely connected at the base by a sort of wing from the partial
rib. Dots of fructification several about the lower part of
each segment, small, round, brown, not reddish. Involucrum
short and oblong, or somewhat square, very delicate, whitish,
jagged or fringed at its edge, affixed laterally to the nerve of
each segment, and separating inwards. It is scarcely umbilicated,
but rather more approaches to the nature of our
Cyathea fragilis, t. 1587, and dentata, t. 1588; yet as there is
some doubt respecting even their genus, and the involucrum
of the present fern has nothing of a cup shape, we rather refer
it, lik e /. 2024, to Aspidium. It does not by any means
agree with the character of Bernhardi’s Cystopteris, Schrad.
New Journ. v. 1. fasc, 2. t. 2, founded on Cyathea fragilis.