21. Dentella J. R. Forster & G. Forster, Char. Gen. Pl. 13. 1775.
小牙草属 xiao ya cao shu
Authors: Tao Chen & Charlotte M. Taylor
Herbs, annual or perennial, prostrate, unarmed. Raphides present. Leaves opposite, usually relatively small, without domatia; stipules persistent, interpetiolar and frequently fused to petioles, triangular, entire to erose, often scarious. Inflorescences terminal or displaced to pseudoaxillary, 1-flowered, ebracteate, subsessile or pedunculate. Flowers bisexual, remarkably reduced. Calyx with ovary portion sometimes papillose-villous with distinctive flattened trichomes; limb tubular, 5-lobed or -toothed. Corolla white to pink, funnelform, inside frequently pubescent in throat; lobes 5, valvate in bud. Stamens 5, inserted at middle or perhaps base of corolla tube, included; filaments short; anthers basifixed or perhaps dorsifixed, included. Ovary 2-celled, ovules numerous in each cell inserted on axile subglobose placentas; stigmas 2, filiform, included. Fruit indehiscent, subglobose to ellipsoid, dry, papery, sometimes papillose-villous with distinctive flattened trichomes, with calyx limb persistent; seeds numerous, small, angled; testa granulate; endosperm fleshy; embryo minute.
About ten species: S Asia to Oceania, with one species apparently adventive in North America; one species in China.
The seeds and capsules of this species were described in detail by Terrell and Robinson (J. Bot. Res. Inst. Texas 1(1): 373-384. 2007).
