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F E R N S OF NORTH AM E R IC A .
shows gradations from a simple frond to those with one pinna
on one side and two on the other.
The venation is so variable that two genera were proposed
by Fée, one for the specimens with free veins, and one for
those with anastomosing veins. Even the careful Mettenius,
who, more than any other botanist, demonstrated the futility
of founding genera upon differences of venation, admitted two
species, Aspidium juglandifoliutn and A . nobile, the first with
anastomosing veins, the second with free veins. In the Texas
fronds the veins are nearly all free, very few anastomosing
near the margin. The Chiapas plants have the venation very
irregular, partly anastomosing and partly free. Other specimens
show a like variability, even on the same pinna, and abundantly
justify Hooker in referring all the forms to one species.
The sori are dorsal on the veins, and form a row each
side of the midrib, and a little distance from it. Outside
of each of these rows is a second row less complete, and
outside of this are often found a few scattered sori. The
indusium is orbicular and peltate, as in the section Polystichum,
but owing to the occasional and sometimes regular reticulation
of the veinlets, the species is referred to the section
Cyrtomiutn, in which Aspidium falcatum, A . cadztcum, and
two or three other species are also placed in Syziofsis Filicum.
Plate LXX V., P'ig. 5-8. — Aspidium juglandifolium, from Chiapas,
Mexico, collected by Gbiesbreght. Fig. 6 is an enlarged portion of a
pinna, showing tbe variable venation. P'ig. 7 is an indusium, and P'ig.
8 is a spore.
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