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2 3 6 FERNS OF N O R TH AMERICA.
months. The pinnæ are lanceolate, and usually broadest at
the base, where they join the rachis by a very short but evident
petiole. They taper gradually to the apex, which is acute
or even acuminate in most specimens, but is now and then
“ rather obtuse,” as Hooker remarks in his work on the British
Ferns. The surface appears smooth ; but careful examination
reveals a slight pubescence along the midribs and veins,
especially on the under surface. The segments are ovate-
oblong, with mostly entire edges, and a rounded or at most
scarcely acute apex ; though the apex often seems acute in the
fertile fronds, on account of the frequently revolute margins of
the segments. The lower segments are rarely enlarged and
pinnately toothed, or lobed. The veins are free. Commonly
the veins fork near the midvein into two divergent veinlets ;
but very often only the lower veins are thus forked, and the
upper ones are simple, as in A . Noveboracense.
The fruit-dots are of small size, and are placed on the
back of the veins, just above the place of forking; or, if the
veins are simple, nearer the midvein than the margin. The
indusium is minute, reniform, and somewhat glandular on
the margin. The spores are oval, and densely muricated.
Plate X X X . — Aspidium Thelypteris. Fig. I is a plant from Salem,
Massachusetts, with two fronds, one of them fertile. The long creeping
root-stock, with several rudimentary fronds rising from it at intervals, is
well represented. Figs. 2 and 3, a sterile and a fertile pinna. Fig. 4,
an indusium. Fig. 5, a spore. The last two figures only are magnified.
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