Stemonaceae

Twining (to several metres long), trailing or erect perennial herbs, mostly with fasciculate tubers, or with a short rhizome. Plants glabrous, or with uniseriate hairs. Leaves papyraceous when dry, alternate, or opposite, or verticillate (China, Japan); blade (elliptic-)ovate or broad-ovate, nerves basal or lateral, curved, shallowly depressed above, secondary intervenation finely trabeculate, leaf margin entire; petiole at base pulvinate (Stemona), or slightly sheathing ( Stichoneuron). In florescences axillary, sessile, or peduncled cincinnae, appearing as short racemes, rarely one-flowered; flowers and bracts often dotted with raphides; bracteoles absent. Flowers consisting of 4 similar segments, representing two rows of two tepals, these free, valvate, out-curved at anthesis, persistent; pedicel articulated. Stamens 4, epitepalous; filaments short, adnate to base of tepals, at base mutually free or shortly connate; anthers consisting of two ovoid or elongate thecae, each opening by a longitudinal lateral slit; the thecae situated on top of the filament, either without ( Stichoneuron) or with an apically enlarged tepal-like appendage of the connective, moreover the connective with a median longitudinal ridge separating the thecae, the ridge either smooth and thin, or fleshy and with a brain-like wrinkled structure, the thecae themselves in addition often protruding into a common sterile appendix, 1-8 mm long, of which the tips may be fused, thus forming a crown-like structure over the stigma (Stemona). Ovary superior or half superior, small, one-celled, ovules few to many, basally (Stemona) or apically (Stichoneuron) attached, anatropous or semi-anatropous; style absent; stigma inconspicuous, roundish, papillose. Fruit a 2-valved capsule; seeds few to many, broadellipsoid, faintly or conspicuously longitudinally ridged; funicle long, with a coralloid, or lobed, hollow, wide-celled aril (Stemona), or aril in the form of uniseriate hairs (Stichoneuron). Endosperm present. Taxonomic position — An isolated family because of various special morphological features of the flower. Its affinity has generally been accepted as being with the Liliaceae s.l., although not closely. Burkill (1960) and Ayensu (1964) suggested an affinity with Dioscoreaceae.