13. Aí/eí?J»a?»=Dorsal-fruitedEerns,having the spore-
cases in a continuous line between the midrib and
margin of the divisions of the frond.
E. DiCKSONiEiE = Eerns whose sori are (in the British
species) produced around the ends of veins projecting
from the margin, and surrounded by an urn-
shaped or two-valved membrane. It contains the
genera Trichomanes and Hymenophyllum.
14. Trichomanes = Marginal-fruited Eerns, having the
s o r i surrounded by urn-shaped expansions of the
frond.
15. Hymenophyllum = Marginal-fruited Eerns, having
the sori surrounded by two-valved expansions of
the frond.
Ü. OsMUNDACEvE = Eerns having the young leaves circinate,
the spore-cases destitute of an elastic ring, and bursting
by two regular valves. It contains the genus
Osmunda.
16. Osmunda = Marginal-fruited Eerns, having the
regular valved spore-cases in irregular, dense,
branching clusters, terminating the fronds.
hi. O p h io g lo s s a c e .® = Eerns having the young leaves folded
up straight, the spore-cases destitute of an elastic ring.
and two-valved. It contains the genera Botrychium
and Ophioglossum.
17. Ophioglossum= Marginal-fruited Eerns, having the
spore-cases sessile in two-ranked simple spikes
terminating a separate branch of the frond.
18. Botrychium = Marginal-fruited Eerns, having the
spore-cases in irregularly branched clusters, on a
separate branch of the frond.
II. CLUB-MOSSES—ZrCOPOii/JCZhA'.
Elowerless plants, bearing spore-cases in the axils of
their leaves, and having reproductive bodies of two
different kinds, but of a similar nature. They consist
of the genus Lycopodium.
19. Zycojsoifia»« = Moss-like plants, with leafy stems,
having the fructifications elevated in terminal
spikes, or in the axils of the leaves.
III. PEPPERWOETS—f f fJ P m W lC PW .
Elowerless plants, bearing axiUary or radical spore-
cases, and reproductive bodies of two dissimilar
sorts. They comprise the genera Lsoetes and
Pilularia.
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