The Afplenium ceterach, Afplenium ruta-muraria, Afplenium
adiantum nigrum, Polipodium fragile, Polipodium
thelypteris, and Polipodium fontanum, in the laft ftages of
their grorvth, become x^crofticha.
In Ofmunda, Lvhofe charaaer is to have the feed-veffels
difpofed in bunches of fpikes at the extremities of die rib of
the fertile leaves, we find the Ofmunda ipicant, wnofe feed-
veifels arc difpofed in lines along the under fide of the lobes,
of the fertile leaves ; and the Ofmunda crifpa, in which they
are placed in lines under the verges of the lobes, wnich aie
gently rolled back upon them as in the Ptens aquilina.
^ It muft offend the tafte of the judicious reader to find the
charaacriftics of the Genera fixed on foundations fo unftcady,
Lvhen he finds plants very diftimilar in their appearance united
; as alfo when he fees a feparation take place between Oi-
munda limaria and Ophiogloffum vulgatum, between Acroftichum
feptentrionale and Afplenium ruta-muraria.
In a family of plants fo nearly approaching in general habit,
and whofe charaacriftic notes are in nature too minute
for our infpeaion, there is no way of acquiring a p eiiea know ledge
of the fpecies, and varieties, but by making careftft and
repeated obfervations upon the plants themfelves, in the natural
places of their growth.
In
In moft of the Britiih proper Ferns the fecdling plants require
a fucceffion of feafons before they produce their fruaifi-
cation. The firft year that a feed vegetates, it produces a fingle
leaf only, which feldom attains to more than one inch in
height, is thin, femi-tranfparent, and moft commonly entire.
The fécond year two or three are produced, one larger than
the other. The third year four or five are produced ; and the
fourth year, more in number, proportionable to the richncfs
and propriety of foil and fituation.
Through this progrefs of growth, the young plants appear
in various ihapes according to die various matter and place in
which they grown When the feeds take root in moift and
fertile foils, in ihaded iituations, on mofty dripping rocks, or
near currents or rills of fpring water, they produce leaves of a
thin, light, femi-tranfparent fubftance. When on dry rocks,
and in barren foils, where they are more expofed to the
air and the fun, the leaves are few in number, ihort, firm,
and opaque. The formicr plants produce larger and more
numerous leaves ; but the latter produce feeds in fewer years
from the firft fpringing up : The firft arc apt to produce
leaves monftrous in ihape or fize ; the laft generally retain
their own proper figure.
The diftcrencc of fize, in confcquence of foil and fituation,
is as remarkable in Ferns as in any other tribe of plants. Wc
frequently fee leaves of Polipodium filix-mas, and Polipodium
b filix