Indigofera udonthaniensis S. Mattapha & P. Chantaranothai, 2013

Mattapha, Sawai & Chantaranothai, Pranom, 2013, Two new species of Indigofera (Leguminosae-Papilionoideae) from Thailand, Phytotaxa 129 (1), pp. 47-52 : 50

Indigofera udonthaniensis S. Mattapha & P. Chantaranothai , sp.nov. ( Fig. 2 ).

Indigofera udonthaniensis can be distinguished from other Thai Indigofera species by imparipinnate leaves, the most non-symmetric T-shaped hairs on the upper surface of leaflets, laxly 15–20-flowered racemes and falcate wing petals.

Type:— THAILAND. Udon Thani, Phu Phrabat , c. 200 m by a nature tail to the north of the headquarters, 17 º 43' 48̎ N, 102 º 21·31.68̎ E, 7 September 2006, Sawai 1042 (holotype BKF!; isotypes BK!, E!, K!, KKU!, QBG!) .

Undershrubs 20–30 cm high with storage roots; twigs with symmetric T-shaped hairs. Leaves imparipinnate, alternately arranged; stipules triangular, 1–2 mm long, apex acute, margin minutely serrate, caducous; petioles 7–10 mm long, hairy; rachis (0.5–) 1–5 cm long, hairy; leaflets 7–15, very rarely 3, oppositely to suboppositely arranged; stipels linear, 0.5 mm long, caducous; petiolules 1 mm long, densely hairy; lamina elliptic, 15–25 × 10–18 mm, apex rounded with mucro 1 mm long, base cuneate, margin entire with hairs; upper surface with the most non-symmetric T-shaped hairs, lower surface with the most symmetric T-shaped hairs, indistinctly reticulate veined; secondary veins 5–8-paired, anastomosing. Racemes 3–6 cm long, axillary, laxly 15–20-flowered, hairy; peduncles 0.5–1 cm long; rachis 2–4 cm long. Flowers 10–12 mm long, pink to purple, caducous; bracts triangular to lanceolate, 1–2 mm long, apex acute, margin serrate, hairy outside, glabrous inside, caducous; pedicels 1.5–2 mm long, densely hairy. Calyx cup-shaped, 1.5–2 mm long; teeth triangular, 0.5–1 × 1 mm, apex acute, margin ciliate, densely hairy outside, glabrous inside. Corolla pink; standard orbicular, 8–10 × 8–9 mm, apex rounded to minutely acuminate, margin ciliate, base rounded, densely hairy on the back, glabrous inside; wings pink to purple, falcate, 7–8 × 2.5 mm, claw 0.5 mm long, apex rounded to minutely acuminate, base oblique, margin ciliate, densely hairy outside, glabrous inside; keel pink to purple, 8–10 × 3 mm, apex acute, base attenuate, margin entire, densely hairy outside; lateral pocket 1 mm long, glabrous. Stamens diadelphous (9+1); staminal tube 6–7 mm long; filaments 0.5–1 mm long; anthers 1 x 0.5 mm, with apiculate, hairy at base. Ovary glabrous, 9–10 mm long, 8–9-ovuled; style c. 2.5 mm long, glabrous. Pods cylindrical, straight, spreading, 30–50 mm long, hairy. Seeds 2–3 × 1.5–2 mm, cylindrical, truncate at both ends, glabrous, yellowish; endocarp blotched between the seeds.

Distribution: —Endemic to Thailand (Ban Phue, Udon Thani).

Habitat & Ecology: —Mixed deciduous forest, elevation of 400– 500 m.

Phenology: —Flowering & fruiting: August to October.

Observations: — Indigofera udonthaniensis is similar to I. reticulata Franchet (1889: 153) by the presence of the most symmetric hairs on beneath of leaflets, the equal number of secondary veins and the subequal length of inflorescence. The species, as opposed to I. reticulata , is easily recognized by indistinctly reticulate veins and upper surface with the most non-symmetric T-shaped hairs. Other characters between the two species are compared and shown in Table 2. This new species was found growing as an undershrub in sandy soils nearby rocky areas, in mixed deciduous forest in association with dipterocarp trees, mostly Shorea siamensis Miq. (Dipterocarpaceae) .

Figures

FIGURE 2. Indigofera udonthaniensis. A: flowering & fruiting twigs, A1: storage roots; B: a floral bud; C: standard in dorsal & ventral views, respectively; D: wings; E: keel; F: stamens without a vexillary stamen; G: ovary; H: pod; I: seed. From Sawai 1042, drawn by M. Norsaengsri.