. r l
■L
lanceolate or oblong-lanccolate, narrowed at the base, especially
the lower ones, and either rounded or subacute at
the apex. The sinuses between them are rounded, and are
gradually narrowed towards the apex of the frond. The
segments are very minutely serrulate 011 the edges; the
smallest ones otherwise entire, and the larger ones either
with sinuous margins or, in large fronds, deeply sinuouspinnatifid.
The texture is herbaceous, the surfaces perfectly
smooth, the color of the upper surface grass-green, of the
lower surface paler and slightly glaucescent. The fronds
wilt very soon after plucking them, and in wilting there is
a slight disposition to fold the segments together, face to
face; for which reason the plant has received the name of
“ Sensitive-Fern.” The first frost of autumn destroys the
sterile fronds; and a late frost in May or June does the same.
The midribs are prominent, and the veins conspicuous; the
latter being copiously reticulated into areoles which enclose
no free veinlets. Along the sides of the midribs and mid-
veins are very long and narrow areoles, and outside of these
are obliquely-placed oblong areoles in several irregular rows.
The fertile fronds are not very common, and a young
botanist may search in vain for them for a long time. They
stand only about half as high as the sterile fronds, and are very
rigid. They are nearly black in color: in winter they dry up,
but remain erect through the next summer, so that a fruiting
plant often has fertile fronds standing of two years’ growth.
The frond is only a few (usually four to six) inches long,
and consists of from four to ten pairs of appressed fleshy or
cartilaginous pinnæ, whxh are divided into a double row of
sub-globose bead-like segments or pinnules; the whole looking
like a small and narrow but dense cluster of diminutive grapes.
Each pinnule has its edges so much recurved that the whole
forms a sort of pouch, apparently filled with sporangia.
Mr. Faxon has made a careful study of the sori, and
has very kindly furnished the account given below.’
The articulations of the sporangia are said by Fée to
be twenty-eight to thirty-two, and more numerous than in any
other fern. I have counted only thirty at most, and more frequently
only twenty-eight. The spores are ovoid and very
dark-colored.
Var. obiusilobata, T o r r e y , Fl. New York, ii., p. 499, t. clx
{Onoclea obiusilobata, S c h k u h r ), is not a permanent variation
of the species, but is based on a not infrequent condition of
the plant, in which the pinnæ of some of the foliaceous fronds
become deeply pinnatifid into obovate segments, which have
mostly free veins and imperfectly developed sori. The indusia
“ ‘ In O. sensibilis the sori are borne on the nii<ldle o f the vein, and consist o f a
tough cylindrical receptacle, three or four diaraetcrs in height, bearing sporangia thickly
all over its surface, and covered when young by a delicate hood-like indnsium, attached
half-way or more around the basc o f the receptacle on the inferior side, and having the
crcnulatc-margined opening toward the apex o f the segment. At an early stage the
blackbcrry-shaped soi'us is almost entirely covered by the indusiiiin, which resembles a
closely drawn cowl, but with the growth o f the sporangia it is thrown back, or rent, and
soon disappears, the sori becoming confluent. The receptacle is very persistent, and may
be seen, covered with the stalks of the sporangia, in the dried lust-year’ s fertile fronds,
which arc always found where the plant grows.”
t Hi
t k i .
' T . i