s * t i6 2 ]
HYMENOPHYLLUM Tunbridgenfe,«
Tunbridge Filmy-leaf.
C R T P 7 0 G A M I A Fillets.
Gen. Char. Fructifications inferted into the margin of
the frond, diftindt. Involucrum two-valved, flat-
tifh, ftraight, opening outwards, longer than the.
Column* Smith Mem. ofi the Furin Acad. Vol. 5.
Spec. Char. Fronds alternately bjpinnate, decurrent*
Iharply ferrated as well as the involucrum. Fructifications
folitary at the upper edge of the bafe
of each general divifion. of the frond.
S yn. Trichomanes Tunbridgenfe. Linn. Sp. PI. 1561.
Hudfi. FI. An. 461. With. B e t. Arr. Vol. 3 .6 5 .
Adiantum petrceum perpufiUum Anglicum, foliis
bifidis vel trifidis. R a il Syn. 123.
G a t h e r e d near Tunbridge by Mr. T. F. Forfter jun.
It grows alfo in Wales, Weftmorland, and the north parts
of Yorklhire, on horizontal moift rocks, which it clothes in
large tufts. Mr. Lightfoot mentions this fpecies as common
in Scotland. The flender wiry roots fpread very far, throwing
out fibres here and there, and producing numerous upright
leaves or fronds, which when fometimes dried up in fummer
curl backwards. Their fubftance is extremely membranous
and pellucid, appearing finely reticulated under a microfcope,
as in all this genus (and in the real Trichomanes), their feg-
ments linear, obtufe, Iharply ferrated, and having a ftrong Ample
central rib. The fructifications, when they occur, take
place of the firft fegment of each pinna or general divifion of
the frond, each terminating its appropriate nerve, and pointing
upwards. Their involucrum is of two flightly concave
valves, arifing from the fubftance of the leaf, irregularly notched
and ferrated in their margin. Between thefe is a fhort
column, befet with fmall round bivalve capfules, each embra-.
ced with an elaftic ring as in the more common ferns.
The bivalve involucrum and fhort column, fo diftin£t from
the urn-fhaped undivided involucrum, and long column or ftyle,
of the true Trichomanes, have induced Dr. Smith to eftablifh
this new genus in his Diflertation on Ferns, printed by the Academy
of Turin. We have attempted to give it an Engliffi,
•name, which is a txanflation of its Greek ones