Sohmaea diffusa (DC. 1825a: 100) H.Ohashi & K.Ohashi (2018b: 161)

Saisorn, Witsanu & Chantaranothai, Pranom, 2022, A taxonomic revision of two genera, Pleurolobus and Sohmaea (Leguminosae) in Thailand and Indo-China, Phytotaxa 573 (2), pp. 231-246 : 237-238

1. Sohmaea diffusa (DC. 1825a: 100) H.Ohashi & K.Ohashi (2018b: 161) .

≡ Desmodium diffusum DC.

Type:— India orient, Lambert s.n. (lectotype G-DC! G00317409 , designated by Ohashi & Xiang-Yun, 2005) .

≡ Hedysarum diffusum [ Roxburgh (1814: 57) , nom. nud.] Roxburgh (1832: 357), non Willdenow (1802: 1180), nom. illeg. Type:— India orient, Roxburgh s.n. (syntypes BM, n.v. & BR! BR0000009894365 [digital image]).

= Desmodium laxiflorum DC. var. formosense Ohwi (1951: 235) . Type :— TAIWAN (Formosa). Fujieda in Kizangun, Okamoto s.n. (holotype KYO, n.v.), fide Ohashi & Zhu (2005).

= Desmodium laxiflorum subsp. parvifolium H.Ohashi & T.T.Chen (1983: 268) . Type:— TAIWAN. Pingtung Co., Mutan , 350–400 m, 26 Oct. 1982, Ohashi et al. 13486 (holotype TUS, n.v., isotypes TAI, n.v., TI, n.v., TUS, n.v.), fide Ohashi & Zhu (2005).

= Desmodium unibotryosum C.Chen & X.J. Cui (1987: 307) , nom. illeg.

Herb, 10–70 cm high; stems and twigs terete, glabrescent or appressed pubescent. Leaves trifoliolate, rarely unifoliolate on lower part of plant, spirally arranged; stipules triangular, 3–10 × 2–3.5 mm, apex long acuminate, curved or straight, surface glabrescent to puberulous; petioles (0.3–) 1.5–2.5 cm long, appressed pubescent and uncinate; rachis 3–10 mm, appressed pubescent and uncinate. Leaflets: stipels filiform, 1.5–3 mm long, apex pointed, glabrescent; petiolules 1.5–2 mm long, pubescent. Terminal leaflet ±elliptic to obovate, 1.5–6.5 × 1–3.5 cm, apex acute to attenuate, base cuneate to obtuse, margin entire, upper surface sparsely straight and uncinate hairy, lower surface densely pubescent; lateral veins 5–7 per side, prominent. Lateral leaflets ±elliptic to ovate, 1–3.5 × 0.5–2 cm, apex acute, base obtuse, margin entire, both upper and lower surfaces like terminal leaflet; lateral veins 5–7 per side, prominent. Inflorescences 10–20 cm long, terminal at both terminal and lateral shoots; rachis straight and uncinate hairy. Primary bract narrowly ovate, ca. 3 × 0.7 mm, apex long acuminate, margin fimbriate, surface pubescent, distinctly veined, enclosing 4-immature flowers and secondary bract. Secondary bract narrowly ovate, 2–2.8 × 0.3–0.5 mm, margin fimbriate, surface pubescent. Flowers ca. 5 mm long, 4-flowered fascicles; bracteoles absent; pedicels 3–4 mm long, with straight hairs on lower most and densely uncinate hairs toward the upper part of pedicel. Calyx dark brownish red, 2.5–3 mm long, base obtuse; outside pubescent, inside glabrous, tube ca. 1.2 mm long; teeth 1–1.2 mm long, ±equal to tube length, upper tooth shallowly divided, ca. 0.3 mm deep. Corolla : standard light blue, wings and keels white; standard broadly ovate, 5.5–6 × 4–4.5 mm, apex emarginate, base attenuate to cuneate, entire at base, claw 1–1.7 mm long; wings slightly oblong to obovate, 4.5–5 × 1.5–2 mm, apex obtuse to rounded, base auriculate, 0.2–0.4 mm long, claw 0.5–0.8 mm long; keels narrowly curved, 4.5–5 × 1.3–1.5 mm, apex acute to obtuse, base auriculate, ca. 0.2 mm long, claw 1–1.8 mm long. Stamens 4.5–5 mm long; anthers ellipsoid, ca. 0.3 × 0.2 mm. Gynoecium 4.5–5 mm long; ovary oblong, sessile, laterally compressed, with minutely hairs, 6–8-ovulate; style 1.5–2 mm long, glabrescent; stigma minutely capitate. Pods indehiscent, 6–8-articulate, oblong, 3–3.5 × 0.2 cm, surface densely uncinate, smooth, upper and lower sutures repand, equally constricted, less than 0.5 mm deep; isthmus ca. 3/5 as broad as the pod; articles linear-oblong, 4–6 mm long, prominently longer than broad; pod stipe ca. 1.5 mm long, glabrescent; fruiting pedicels 3–4 mm long, pubescent, with straight hairs on lower most and densely uncinate hairs toward the apex. Seeds transversely oblong.

Distribution:— India, Nepal, Bhutan, Myanmar, China, Taiwan, Thailand, Indonesia, Philippines, and Papua New Guinea.

Ecology:—Open areas of deciduous and bamboo forests; ca. 635 m elev.

Phenology:—Flowering in September–October. Fruiting in October–November.

Specimens examined:— THAILAND. Chiang Mai: Mae Rim, Doi Suthep , 1 Oct. 1988, Maxwell 88-1161 ( CMU, L) , Samoeng, Karen village , 11 Oct. 2001, Maxwell 01-522 ( CMUB) & Mae Rim, Mae Sa Botanical Garden , 5 Oct. 1989, Pooma 372 ( BKF) ; Nan: Doi Phu Kha , 31 Oct. 2013, Clark et al. 303 ( K) ; LAOS. Houa Phan: Na Ham, Sam Neua , 14 Sept. 1920, Poilane 1851 ( AAU, BKF, L, P-2 sheets) ; Entre N. Dlet et M. Seng Traminh, 800–1000 m, 13 Sept. 1929, Poilane 16940 ( P) ; 240 Km de la route de Vinh au Tanninh , 1500–1600 m, 30 Aug. 1929, Poilane 16790 (P-2 sheets) ; VIETNAM. Tonkin: Moc Ha , 10 Oct. 1891, Balansa 4493 ( P) , without locality, Oct. 1887, Balansa 2205 ( P) , Tonkin Occidental, Bon 6070 (P-2 sheets), Tonkin Occidental, Bon 6071 (P-2 sheets) & Tonkin Occidental, Bon s.n. ( G) ; Hanoi: Nam Cong , 18 Nov. 1891, Bon 4923 (P-4 sheets) ; Lao Cai: route de Lao Kay à Chapa , 200–1400 m, 25 Sept. 1943, Petelot B. 390 (P-2 sheets) & entre Bao Nhai et Pakha , 500–600 m, 10 Dec. 1935, Poilane 25021 (P-3 sheets) ; Yen Bai: Bao Ha , 21 Feb. 1936, Poilane 25248 ( BKF, P) ; Hoa Binh: Cho Bo , 15 Nov. 1887, Balansa 2194 ( P) ; Nghe An: Pu Mat, Khe Bu , 17 July 1998, Khoi C 556 ( HNU) & Pu Mat, Khe Bu , 17 July 1998, Khoi C 557 ( HNU) ; Ba Ria-Vung Tau: Long Son, Quan Ho , 20 Oct. 1911, Lecomte & Finet 11 ( P) .