1. Mitragyna diversifolia (Wallich ex G. Don) Haviland, J. Linn. Soc., Bot. 33: 71. 1897.
异叶帽蕊木 yi ye mao rui mu
Nauclea diversifolia Wallich ex G. Don, Gen. Hist. 3: 467. 1834; Stephegyne diversifolia (Wallich ex G. Don) J. D. Hooker.
Trees, perhaps deciduous, to 15 m tall; branches angled becoming terete, pilosulous to glabrescent. Petiole 5-15 mm, glabrous, puberulent, or pilosulous; leaf blade drying papery, ovate-oblong to elliptic-ovate, 6-14 × 3-9 cm, adaxially glabrous, abaxially sparsely to densely pilosulous or tomentulose, base rounded to cordulate, apex obtuse to shortly acuminate; secondary veins 8 or 9 pairs, strongly ascending, sometimes with pilosulous domatia in abaxial axils; stipules elliptic-oblong to ovate, ca. 2.5 cm, strigillose to glabrous, abaxially weakly to strongly keeled and pilosulous, apex obtuse to rounded. Inflorescence densely pilosulous or strigillose to glabrescent; peduncles 1-3 mm (i.e., portion above articulation of subtending leaves but not including entire growth of branch); flowering heads 3 to numerous, 8-10 mm in diam. across calyces, 13-20 mm in diam. across corollas; bracteoles linear-spatulate, ca. 3 mm, glabrous to sparsely ciliolate. Calyx glabrous; ovary portion obconic, ca. 1.5 mm; limb ca. 1.5 mm, subtruncate to lobed for up to ca. 1/2; lobes triangular, obtuse. Corolla yellowish white, outside glabrous, inside densely pilosulous in throat and on lobes; tube ca. 3 mm; lobes triangular, ca. 2.5 mm, acute. Fruiting heads 8-10 mm in diam. Capsules 3-4 mm, with persistent calyx limb markedly thickened; seeds 1-2 mm. Fl. [Feb, Jul, Aug], fr. [Jan, Mar, Dec].
Forests; [300-400 m]. Yunnan [Cambodia, Indonesia, Laos, Malaysia, Myanmar, Philippines, Thailand, Vietnam].
This species seems to be similar to and at least sometimes confused with the commonly collected Mitragyna parvifolia (Roxburgh) Korthals; these species differ at least in their corollas, with the tube 5-6 mm and substantially longer than the lobes ca. 2 mm in M. parvifolia, vs. the tube ca. 3 mm and less than twice as long as the lobes ca. 2.5 mm in M. diversifolia. Ridsdale (Blumea 24: 63-65. 1978) reported a difference in the distribution of these, with M. parvifolia primarily found in India and Sri Lanka and M. diversifolia to the north and east of this, including China. Puff et al. (Rubiaceae of Thailand, 46. 2005) noted that in Thailand M. diversifolia is most often found in deciduous vegetation and is common in secondary vegetation, in particular in edges along fields.