on: Sensitive Fern. Gradations from Leaf to Fruit.
_Obtusilobata_ Form]

(1) SENSITIVE FERN. _Onoclea sensibilis_

Fronds one to three feet high, scattered along a creeping rootstock,
broadly triangular, deeply pinnatifid, with segments sinuately lobed or
nearly entire. Veins reticulated with fine meshes. The fertile fronds
shorter, closely bipinnate with the pinnules rolled up into berry-like
structures which contain the spore cases. (The name in Greek means a closed
vessel, in allusion to the berry-like fertile segments.) The sensitive
fern is so called from its being very sensitive to frost. The sterile and
fertile fronds are totally unlike, the latter not coming out of the ground
until about July, when they appear like rows of small, green grapes or
berries, but soon turn dark and remain erect all winter, and often do not
discharge their spores until the following spring. The little berry-like
structures of the fertile frond represent pinnules, bearing fruit-dots,
around which they are closely rolled. As Waters remarks, "Most ferns hold
the sori in the open hand, but the sensitive fern grasps them tightly in
the clenched fist."

Var. _obtusilobata_ is an abortive form with the fertile segments only
partially developed. The illustration shows several intermediate forms.

[Illustration: Sori of Sensitive Fern]

[Illustration: Sensitive Fern. _Onoclea sensibilis_]

[Illustration: Sensitive Fern, Fertile and Sterile Fronds on one
Stock _Onoclea sensibilis_ (From the collection of Mr. and Mrs. L.P.
Breckenridge)]

[Illustration: Ostrich Fern. _Onoclea Struthiopteris_. Fertile Fronds]

(2) OSTRICH FERN

_Onoclea struthiopteris_. PTERETIS NODULOSA

_Struthiopteris Germanica_. _Matteuccia struthiopteris_

Fronds two to eight feet high, growing in a crown; broadly lanceolate,
pinnate, the numerous pinnae deeply pinnatifid, narrowed toward the
channeled stipe. Fertile fronds shorter, pinnate with margins of the pinnae
revolute into a necklace form containing the sori.

[Illustration: Ostrich Fern. Sterile Fronds (New Hampshire)]

The rootstocks send out slender, underground stolons which bear fronds the
next year. Sterile fronds appear throughout the summer, fertile ones in
July. Seen from a distance its graceful leaf-crowns resemble those of the
cinnamon fern. An intermediate form between the fertile and sterile fronds
is sometimes found, as in the sensitive fern. This handsome species
thrives under cultivat