Gomphostemma microdon Dunn

Erect herb up to 1 m tall. Stems robust, obtusely quadrangular, with dense stellate hairs; internodes straight. Leaoes petiolate, spreading, chartaceous; blades elliptic, elliptic-ovate or obovate, 13 – 23 × 3 – 9 cm, apex acute, margin serrate, base cuneate, upper side dark green with sessile stellate hairs, lower side pale green tomentose with dense stellate hairs and dendroid hairs confined on midrib and veins; petioles 20 – 33 mm long. Inflorescence axillary, raceme-like, elongated, lax with axis visible between cymes, unbranched, 30 – 80 mm long with opposite cymes reduced, inserted at the upper nodes at which leaves are usually present; verticils 1 – 2 - flowered, subtended by the upper leaves; peduncles 20 – 50 mm long, with dense stellate hairs; bracts exceeding calyx, elliptic or broadly ovate, 13 – 20 × 6 – 9 mm, apex acute, margin shallowly serrate, base cuneate, with stellate hairs on both sides; bracteoles obovate, 5 – 10 × 1 – 2 mm, with dense stellate hairs on both sides. Flowering calyx greyish-light green, infundibular, 3 – 8 mm long, 10 - ridges; tube 2 – 6 mm long, outside with dense stellate hairs, inside glabrous; lobes short triangular, 1 – 2 mm long, apex acute, margin marginate, outside with dense stellate hairs, inside with adpressed simple hairs. Fruiting calyx infundibular, 3 – 5 mm long; tube 2 – 6 mm long; lobes triangular, c. 1 mm long, apex acute, margin marginate. Corolla yellow or reddish-yellow, (13 –) 20 – 23 (– 33) mm long, throat inflated, abruptly dilated near the throat, outside with stellate hairs, inside with an annulus of simple hairs; tubes slender, slightly incurved, 20 – 23 mm long; posterior lip semi-circular, 2 – 3 mm long; anterior lip 3 - lobed, spreading; median lobe broadly ovate, 5 – 10 × 3 – 10 mm, slightly undulate; lateral lobes ovate, apex round. Staminal filaments slightly fleshy. Style slender, glabrous with apex unequally lobed. Nutlets 1 – 2, elliptic-ovate, 2 – 3 mm long, tomentose.

DISTRIBUTION. China (Yunnan), Vietnam, Thailand, Laos. Map 5. SPECIMENS EXAMINED. CHINA. Yunnan. Menglun, Mengla [21.2665 °, 101.3833 °], 15 Sept. 1983, Sino-American Expedition to Yunnan 191 (KUN 2 sheets); Che-li Hsien, 930 m, Aug. 1936, Wang 53323 (holotype of Gomphostemma deltodon, PE); Szemao, W Forest, 1330 m [2300 ft], Henry 12301 (holotype of G. microdon, K; isotypes K, NY). VIETNAM. Hoa Binh. Mai Chau, Hang Kia [20.665 °, 103 °], 3 Oct. 2000, Phuong 3319 (HN 3 sheets); Son La. Phu Yen? istr. [21.1995 °, 102.5883 °], 9 Aug. 2009, Cuong & Cuong 2093 (HN 2 sheets); Moc Chau [21.833 °, 102.53 °], 13 April 1988, Phuong 29 (HN 2 sheets); UNLOCALISED. Lemarie s. n. (P 2 sheets); 3 alansa s. n. (P). LAOS. Sayabouly. Pak Lai [18.2 °, 101.2165 °], 1866 – 1868, Thorel 3362 (P 2 sheets); UNLOCALISED. Counillon s. n. (P). THAILAND. Chiang Mai. Jawm Tong [Chom Thong], Mae Soi Subdistr. [18.2565 °, 98.6356 °], Mae Soi Valley, 223 m, 11 Nov. 1990, Maxwell 90 - 1238 (AAU, L); Nan. Phu Ka [19.1992 °, 101.0569 °], 200 m, 28 Aug. 1938, Somkid 151 (BKF). HABITAT. In disturbed deciduous forest, limestone area, 200 – 1330 m. CONSERVATION STATUS. Gomphostemma microdon has been regularly collected from the field. However, an AOO of 22 km 2 falls under EN and the EOO of 236,582.12 km 2 under LC. The Least Concern (LC) category is applied. PHENOLOGY. Flowering and fruiting April – November. NOTES. Gomphostemma microdon is a remarkable species recognised by having short calyx lobes, 1 – 2 mm long, and spreading inflorescence with bracts exceeding calyx. It is morphologically similar to G. dolichobotrys and G. repentum by having an unbranched, racemelike inflorescence. Wu circumscribed G. deltodon on the basis of its slightly larger calyx (Wu 1963). However, calyx length is variable throughout the distribution of this species.