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F ERN S OF NORTH AMERICA.
much more deeply incised than any other which I have seen,
was collected by Mr. F. Bourquin, near Pemberton in New Jersey,
in 1867. In this frond the incisions are so deep as to
render the pinnæ fairly pinnatifid.
The two lowest pinnæ of the frond are very often exactly
opposite, and considerably deflexed : in the living plant they
have the upper surface nearly horizontal, and are directed forward,
side by side, nearly at a right angle to the rachis. The
next two or three pairs are less exactly opposite, and less plainly
deflexed. The remaining pinnæ are regularly alternate, and
commonly show a slight upward curvature, rendering them somewhat
scythe-shaped. The lower pinnæ are but very little shorter
than those in the middle of the frond.
The veins of the sterile frond are free, as they are generally
in the true Polystichoid Aspidia. Each vein is pinnately, rather
than dichotomously, divided into about four veinlets, of which
the lowest one is on the upper side of the vein. The midvcin
of the pinna, and the principal vein of the auricle are marked
by a slight channel on the upper surface of the frond, but the
veinlets are not conspicuous until the frond is dried, and are
then most easily seen by holding up the specimen against the
light.
In the fertile fronds, which are often rather taller, or at
least more erect, than the sterile, the upper third part of the
frond is suddenly contracted, so that the lowest fertile pinna is
not more than two-thirds as long or wide as the sterile pinna
next below it. The sori are borne near the midvein, either on
à
FERN S OF NORTH AMERICA.
the lowest veinlet of each group, or on the two or three lower
veinlets. A somewhat unusual thing in Aspidium occurs m
the present species; the sori being mostly borne at the ends
of the veins, which are enlarged into oval receptacles, much
as in Polypodhm. This peculiarity was observed by Dr.
Mettenius, who says simply “ son terminalii’ In A . mumtum
many of the sori are also terminal on the veins, but m A .
Lonchitis they seem to be uniformly dorsal. It is also noteworthy
that the veinlets of a fruiting pinna are not uniformly
free, but tend to form irregular scattered areoles.
In var. incisum there is no sudden transition from ample
sterile pinnæ to contracted fertile ones, but nearly or quite all
the pinnæ of the fertile frond are soriferous, the sori pretty
much covering the upper pinnæ, but confined to the tips of the
lower ones.
The indusium is orbicular and peltately attached at the
centre : its margin is obscurely crenulate, but devoid of glands.
The cellules of which it is composed have sinuous margins, and
are arranged in lines which radiate from the centre. The pedicels
which support the sporangia lengthen as the fruit ripens, so
that at last the sporangia form one confluent mass on the back
of the fertile pinnæ, looking not unlike the massed fructification
of an Acrostichum, a resemblance which suggested to
Michaux the specific name of the fern. I find fourteen or
fifteen joints in the ring of the sporangia. The spores are
ovoid or bean-shaped, and have a conspicuous irregular winglike
border.
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