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FERNS OF NORTH AMERICA. 159
have distinct stalks from half an inch to an inch and a half long.
The stalks of the side divisions join that of the middle division
by a slight articulation. The middle division is considerably
wider than the others, broadly and symmetrically triangular in
shape, and is composed of several pairs of opposite sessile bipinnatifid
pinnæ, the "lowest of which is the largest, though
much smaller than the stalked primary divisions below it. The
two lateral primary divisions are also broadly triangular, but are
not symmetrical, as the lower side of each is much more developed
than the upper. The pinnæ of these are usually opposite,
though not invariably so, and are once pinnatifid. The first
pinna on the lower side of a lateral primary division is commonly
equal in size and similar in cutting to the second pinna
of the middle primary division. The lobes of all the pinnæ arc
oblong, obtuse, slightly curved upwards, and vary from entire to
crenate or toothed, according to their size. Every lobe has a
midvein, from which the veinlets proceed on either side. The
veinlets are either simple or forked, and bear the small roundish
naked fruit-dots near the margin of the lobes.
The sporangia are smooth ; and the spores, which arc beanshaped,
are furnished with scattered warty prominences.
Closely allied to this species is the Phegopteris calcarea of
Fée. It is more rigid in habit, has proportionately smaller lower
pinnæ of the primary lateral divisions, and is everywhere dotted
with minute sessile glands. It is found in Europe and A sia ;
and, though it has frequently been attributed to America also, I
ha\-c never been so fortunate as to see an American specimen,
and am persuaded that none has ever been discovered.
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