J r J
The sori are oblong, and extend nearly from the mid-
vein to the margin. Though mostly single, and confined to
the upper side of the fruiting veinlet, the lowest one of a
lobe is often double or diplazioid, and such double sori are
almost always found on the long and slender tips of the
pinnæ.
The indusia are of a rather firm texture, moderately
vaulted or convex, and when young give to the lower sur.
face of the frond a silvery sheen, whence the common name,
given, as it appears, by Dr. Jacob Bigelow.
The spores are bean-shaped, and are irregularly and narrowly
winged.
This fern is not closely related to any other occurring
within our limits, but there are several in Asia, or in tropical
America, which more or less closely resemble it.
Plate L. — Asplenium thelypteroides. The specimen drawn was
collected near New Haven, Connecticut. Fig. 2 is a lobe of a pinna,
and Fig. 4 the apex of a pinna, the latter showing the diplazioid sori.
Fig. 3 is a spore.
