ADDITIONS TO “RUBIACEAE OF THAILAND. A PICTORIAL GUIDE TO INDIGENOUS AND CULTIVATED GENERA”
Distribution.— NORTHERN: Chiang Mai [Doi Suthep, types H. bracteata: Kerr 1145, 1792], Chiang Rai, Nan, Lampang, Phrae, Uttaradit, Sukhothai, Kamphaeng Phet; NORTHEASTERN: Phetchabun, Loei, Nong Khai; EASTERN: Chaiyaphum; SOUTHWESTERN: Kanchanaburi, Phetchaburi; SOUTHEASTERN: Prachin Buri.
Notes. — Hyptianthera stricta is variable in both vegetative features and characters in the fertile region. Hyptianthera bracteata, once described as a Thai endemic (Craib, 1911, 1932), cannot be upheld as a separate species on the basis of longer stipules and bracteoles.
The genus/species is part of a well-circumscribed but relatively ill-known group of closely allied genera which also includes Hypobathrum (syn. Petunga) and the Indochinese Xantonnea. Deb’s (1989) proposal to merge Hyptianthera with Hypobathrum is not generally accepted and not followed here because more detailed work on this complex group needs to be carried out.
Field studies corroborate that the taxon is a facultative rheophyte, confirming van Steenis’ (1981: 355) doubts whether the plant a “strict” (obligate) rheophyte. It typically grows in sandy banks along streams or in rocky areas around or in streams, not uncommonly together with other rheophytes such as Kailarsenia lineata (Rubiaceae) or the more common Homonoia riparia (Euphorbiaceae). Its riverine habitats are normally found in areas of dry evergreen and seasonal rain forest, but occasionally also in dry dipterocarp forest and pine forest (then often restricted to shaded gullies). The plants, however, also survive away from streams and rivers. Detailed information on herbarium labels is often too poor and imprecise to get an idea of the actual habitat situation.
Morindopsis Hook.f. in Benth. & Hook., Gen. Pl. 2: 93. 1873.
Shrubs or treelets, dioecious. Leaves opposite (decussate), shortly petiolate; stipules triangular. Inflorescences often paired and mostly distinctly supra-axillary, (long) pedunculate, consisting of much congested, several- to few-flowered cymes; each cyme subtended by a pair of bracts (sometimes uniflorous in females). Flowers 4–5-merous, subsessile, in the axils of minute bracteoles. Calyx with small lobes. Corolla hypocrateriform, tube pilose at the throat, lobes contorted in bud, spreading in open flowers. Stamens inserted just below the throat; anthers subsessile, their tips somewhat exserted from the throat (in males; sterile anthers much reduced and included in females). Ovary crowned by a ring-like disk, 2-celled, each locule with a multiovulate peltate placenta attached to septum; the common style with 2 at least basally hairy, filiform stigma branches slightly exserted from the throat (in females; ovary much reduced and empty in males, the rudimentary stigmas short and included). Fruits indehiscent, with a leathery skin (not conspicuously fleshy), elongated, crowned by the persistent and slightly enlarged calyx lobes; each of the two locules with numerous, imbricately arranged seeds.
A monotypic genus belonging to tribe Octotropideae (syn. Hypobathreae) and recorded from NE. India to Indochina.— See notes below.
Morindopsis capillaris (Kurz) Kurz, J.Asiat. Soc. Bengal, Pt. 2, Nat. Hist. 43(2): 189. 1874, Kurz, Forest Fl. Burma 2: 52. 1877; Hook. f., Fl. Brit. India 3: 121. 1880; Pit. in H.Lecomte, Fl.