CHAPTER V.
SYNOPTICAL TABLE OF GENERA.
T h e few genera wliioli are represented among tho British Forns,
afford so inadequate an illustration of any particular system of classification,
that thoir sequcnco bocomos altogether unimportant. In
our Index Filicum we have attempted an arrangement of the entire
family of Ferns, on tho plan which has been explained in the foregoing
pages ; and this arrangement we follow here in its loading
features, that is, in so far as respects the principal groups ; but as
regards the sectional subdivisions of these groups, which give the
actual sequence of genera, it will bo more convenient here to follow
the order adopted in other works on British Ferns, especially
in our Handhook o f British Ferns, and in the Folio edition of the
present work. Tho sectional groups aro the samo as those of the
Index Filicum, their relative position only having been changed.
N a t t i b a l O r d e r POLYPODIACEÆ, o r T r u e F e r n s .
The Ferns belonging to this Order have their fronds oiroinate in
vernation ; their fructification dorsal or marginal ; and their spore-
oases furnished with an elastic jointed ring.
• SPORE-CASES NOT VALVATE.
T e i e e I.—Polypodineæ.— FrucUfieaUmi dorsal; spore-cases without valves,
bursting irregularly and transversely ; ring vertical, nearly complete.
§ i-— PoLYPODiEÆ.— Sori round, naked, i. e. without proper indusia or seale-
like covers, dorsal on the veins.
1. Polypodium.—Sori punotiform, round or roundish, exposed on
the piano under surface of tho frond.
2. AUosorus.—Sori round or suh-obloiig, becoming laterally confluent,
hidden beneath tho scarcely attenuated roflexod
margins of tho frond.
§ u.-GYMNOGEAMMEiB.-Sori linear, parallel with the veins, naked, i. o.
without indusia, dorsal on the veins.
3. Gymnogramma.—Sori linear, forked below; (an annual or
biennial Fern).
Cb t e ea o ii wh icli h a s lin o a r sori, also h a s th e h id u s ium obsolete,
so a s to s im u la te n a k e d lin o a r masses. See th is gemis
u n d e r § iv . A s p ie n ie « .
§ iii,_A sP iD iE ® .—S o ri punctiform, rotundale, covered while youmg by seah-hke
indusia o f the same form, dorsal on fJie veins.
4 . P o ly s t i c h u m .— Sori covered by circular peltate indusia, attached
at their centre.
5 . Lastrea.—Sori oovorod by roniform indusia, attached at the
notch on their indented posterior side.
§ i v .-A s P L E N iE « .- S o r i oblong or linear, covered while young by seale-like
indusia o f the same form, lateral on the veins.
6. AtLyrium.—Sori oblong, Innately curved, sometimes (especially
the basal ones) Mppoorepiform or horse-shoe-shaped,
the indusia attached along their concave edge, the free
margin fringed ; venules free.
7 . A s p l e n i u m . - S o r i simple, linear or oblong, oblique; venules
free.
8 . S c o l o p e u d r i u m . - S o r i double, i.e. in proximate oblique parallel
pairs face to face, covered by elongate straight mdusia,
wHoh open along the centre of tho double or twin sorus ;
venules free.
9 C e t e r a c l i . - S o r i simple, oblong, scattered, growing from tbe
anterior side of the veins (except the lowest on each pinna
which is on the posterior side), hidden among imbricated
cbaffy scales ; indusium obsolete ; venules reticulated.