2. Onoclea Linnaeus, Sp. Pl. 2: 1062. 1753; Gen. Pl. ed. 5, 484, 1754.
Sensitive fern [Greek onos, vessel, and kleiein, to close, in reference to the sori, which are enclosed by the revolute fertile leaf margins]
David M. Johnson
Plants terrestrial. Stems creeping, stolons absent. Leaves strongly dimorphic, fertile leaves usually shorter, greatly contracted, persistent 2--3 years, sterile leaves dying back in winter. Petiole of sterile leaf ca. 1--1.5 times length of blade, petiole of fertile leaf 2--6 times length of blade, bases swollen and persisting as trophopods over winter; vascular bundles 2, lateral, lunate in cross section. Blade of sterile leaf deltate, pinnatifid to pinnate-pinnatifid proximally, reduced and shallowly pinnatifid distally, herbaceous to papery, blade of fertile leaf linear-oblong, 2-pinnate, leathery. Pinnae not articulate to rachis, segment margins of sterile blades entire to sinuate or shallowly lobed, margins of fertile pinnules strongly revolute and forming hardened beadlike structures; proximal pinnae largest or nearly so, sessile or adnate, equilateral; costae adaxially flat; indument on both sides of linear to lanceolate scales and/or multicellular hairs on rachis and costae. Veins reticulate with areoles lacking included veinlets in sterile leaves, veins free in fertile leaves. Sori covered by strongly revolute margins of pinnae, ± round; indusia vestigial, triangular, persistent but not easily seen in mature leaves. Spores greenish, with a few low folds and numerous, minute, echinate-cristate elements. x = 37.
Species 1 (1 in the flora): temperate regions in Northern Hemisphere, Asia.
Onoclea is one of several genera known to store starch grains in long-persistent petiole bases (trophopods) (W. H. Wagner Jr. and D. M. Johnson 1983).