8. Diplodiscus Turczaninow, Bull. Soc. Imp. Naturalistes Moscou. 31: 235. Jun-Ju. 1858.
海南椴属 hai nan duan shu
Hainania Merrill; Pityranthe Thwaites (Nov-Dec 1858).
Trees or shrubs. Leaves simple, entire, long or shortly petiolate; stipules minute, caducous; leaf blade ovate-orbicular, base asymmetrical, usually cordate, basal veins 5-7, margin entire, slightly sinuate, or minutely denticulate distally; foliar nectaries absent. Inflorescences terminal, paniculate. Flowers bisexual. Bracts minute, caducous. Involucral bracts absent. Calyx campanulate, 2-5-lobed, lobes unequal in length. Petals 5, oblanceolate. Stamens 20-30, free or slightly connate in 5 fascicles; filaments long; anthers minute, 2-thecate, anther cells not connate; staminodes 5, opposite to petals, lanceolate. Ovary syncarpous, superior, 5-loculed; ovules up to 5 per locule; style slender; stigma pointed. Fruit a capsule, obovoid, 4-5-angled, loculicidally dehiscent [?sometimes indehiscent]. Seeds 1-3 per cell, sometimes reduced to 1 per fruit, glabrous, scaly, or hairy.
Nine or ten species: China, Borneo, Malaysia, Philippines, Sri Lanka; one species (endemic) in China.
A close morphological relationship between Diplodiscus, Hainania, and Pityranthe has long been recognized, and various pairs of these three genera have been synonymized. Merrill distinguished Hainania from Pityranthe, represented by a single species endemic to Sri Lanka, on the basis of Hainania having more numerous ovules and hairy seeds. Diplodiscus was separated from Hainania and Pityranthe by the fruit, which contains only one (rarely two) glabrous seeds. Kostermans (Reinwardtia 5: 372. 1961), followed by Meijer and Robyns (Rev. Handbook Fl. Ceylon 7: 428-430. 1991), reduced Pityranthe to synonymy under Diplodiscus, which has priority by about five months. Bayer and Kubitzki (Fam. Gen. Vasc. Pl. 5: 258. 2003) made Hainania a synonym of Pityranthe and thus also of Diplodiscus.