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hexagon. It rarely happens that the wing is interrupted between
the first and second pairs of pinnæ.
The fronds are thinly herbaceous in texture, slightly
hairy on both surfaces, but more so on the under surface,
where there are also found a few minute ciliate scales along
the midribs and principal veins.
The veins are pinnately arranged and free. Fertile fronds
bear sori on every segment. The sori are rather small,
round and naked, and are borne on the back of the veinlets
just below the apex. The lower veinlets of each segment or
lobe bear their sori quite remote from the margin, while the
upper veinlets bear theirs near the margin. The sporangia
have a ring of about fifteen articulations. On many, perhaps
all, of the sporangia, there are a very few (2-4) unicellular
hairs, which are found on the sides of the sporangium near
the end, but not on the ring. Mettenius says there is one
bristle-like and one gland-tipped hair each side of the ring;
but my observations tend to show that the hairs may be all
slender or all gland-tipped, and that in many sporangia they
are entirely lacking. When the sporangia have been boiled on
a glass slide they shoAV the modified cellules of the side opposite
the ring with great distinctness, and the two transversely
elongated cellules which separate when the sporangium opens
are especially worth examination. The spores are bean-shaped,
amber-colored, and marked with a single vitta.
This fern is so closely related to P. polypodioides that it
is often difficult to decide to which species a given specimen
should be referred. In general the plant here described is
much larger than the other, and has fronds much more
broadly triangular. The lowest pinnæ in P. hexagonoptera
are decidedly longer and broader than the next lower pair,
while in P. polypodioides the difference between the lowest
pinnæ and the next is very little; in fact the lowest pinnæ
are sometimes even shorter than the next ones. P. hex-
is more southern in its range than P. polypodifor
it is not a common plant in Canada, but extends
to the Gulf of Mexico, while P. polypodioides is found far
beyond the Arctic Circle, but docs not occur, I believe, south
of Pennsylvania and Ohio. Nothing like our present fern
is found in Furope, where the other species is common
enough.
The genus was proposed in 1851 by Fée, and
distinguished from Polypodium by having the sori dorsal on
the veins, and not at the enlarged apices of the veins. He also
pointed out a difference in the general habit and in the number
of vascular bundles in the stalk. The genus was accepted
by Mettenius, who added to it the species having
anastomosing veins, which had been excluded by Fée. He
discovered other distinctions from Polypodium in the want
of an articulation at the base of the stalk, and in the acute
and not enlarged tips of the veinlets. In all these characters,
with the sole exception of uncovered sori, Phegopteris is absolutely
identical with A sp idium ; and since there are many species
in which the indusium is said by one author to be present.
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