Mucuna laticifera Ingalhalikar, N V Page & Gaikwad, 2017

Ingalhalikar, Shrikant, Page, Navendu & Gaikwad, Swaroopsingh, 2017, Mucuna laticifera, a new species from north-eastern India, Phytotaxa 319 (1), pp. 118-122 : 118-121

Mucuna laticifera Ingalhalikar, N V Page & Gaikwad , sp. nov., Figs. 1 & 2

Type:— INDIA. Sikkim: North Sikkim district, Kabi, 23 km from Gangtok on N. Sikkim Highway, 27.40405 N, 88.61747 E, 1550 m, 20 th June 2016 (with flowers and fruits). Swaroopsingh 040 (holotype K!, isotype SUK!)

Diagnosis:— Mucuna laticifera is similar to M. macrocarpa and M. birdwoodiana with respect to habit, type and position of inflorescence and large, woody nature of the pod. However, it can be distinguished from both these species based by the presence of a watery latex, distinctly pedunculate side branches of the inflorescence, persistent bracteoles that are longer than the calyx, glabrous standard and wing petals and pod margins that are parallel without constrictions between the seeds.

Description: —Large woody climber; stem 10–20 m long, 5–12 cm diameter; bark dark brown, soft, lenticellate; branches slender, glabrous, exuding watery latex when cut. Leaves 25–30 cm long; petiole 8–12 cm, grooved; stipules lanceolate, 0.7–1.0 cm, glabrous; stipels not persistent; terminal leaflet ovate, cuneate, 15–18 × 7–9 cm, acumen 2.0– 2.5 cm; lateral veins 8–10 pairs, merging into margins; petiolules 1 cm; lateral leaflets 14–17 × 6–8 cm, oblique with width ratio of 5:3; leaflets entire, membranous, glabrous. Inflorescence from old branches, falsely racemose, 20–30 cm long, flowers well spaced; peduncles 0.8–1.2 cm; bracts obscure; pedicels 1–3 fascicled on lateral peduncles; bracteoles ovate, acute, 1.5–2.0 cm, brown with pale bands, persistent; calyx greenish brown, covered with pale deciduous bristles, tube 8–12 mm long, lateral lobes 8–10 mm, lower lobe 10–15 mm. Corolla strongly odorous (like over ripe fruit), uniformly greenish during the early stages and turning pale yellow with age; standard, wings and keel up to 4, 6 and 6.5 cm, respectively, keel apex horny. Stamens 10, diadelphous (9+1), dimorphic; staminal tube 4–5 × 0.6 cm, glabrous; lower 6 stamens with basifixed 3 mm long anthers, upper 4 stamens with dorsifixed 1–2 mm long anthers; filaments of united stamens 1.5–2.0 cm long, that of free stamen 5.0– 5.5 cm long. Ovary 2.5–3.0 × 0.3 cm with 1 mm wide ridge along the margin, covered with greenish yellow soft hairs, style 4.5–5.0 cm, glabrous; stigma 1 mm, penicillate. Pod linear, straight, 25–40 × 4.0– 4.5 cm, 8–10 mm thick, woody, with irregular ridges along margins, pod segments rectangular, apex rounded; covered with dense brown stiff deciduous hairs. Seeds 8–15, smooth, black, rounded on 3 sides and flat on fourth side, depressed at the center, 2.0 × 2.5 cm, 7–10 mm thick, hilum black, ¾ of seed circumference.

Additional specimens examined:— INDIA, Sikkim, Soreng sub district, 1314m, 27.22841 N, 88.20301 E, 1314 m, 20 June 2016, Swaroopsingh 050 ( BSHC!) ; West Bengal, Darjeeling district, Ghoom , 27.01304 N, 88.19802 E, 1800 m, 27 April 2016, Swaroopsingh 045 ( SUK!)

Phenology:— Flowering - March to June, Fruiting—September to March.

Etymology:— The specific epithet laticifera refers to the presence of a watery latex in the branches.

Distribution and associated species:— This species is so far known from only three localities, two of them in West and North Sikkim districts and one in the Darjeeling district of West Bengal. It is fairly abundant in the evergreen montane forests between 1300–2000 m elevation in shady under canopy of large trees in association with species of Symplocos Jacq. (1760: 24) , Ilex L. (1753: 125), Styrax L. (1753: 444) and Ficus L. (1753: 1059).

Interrelationships and critical notes:— Mucuna laticifera is morphologically closely related to M. macrocarpa and M. birdwoodiana in having large inflorescences from old stem and laterally flattened large woody torulose pods that are more than 40 cm long.The similarities and differences between the three species are summarized in Table 1.

Wilmot-Dear (1987) in her revision of the genus Mucuna from the Indo-Burmese region, cites a collection made by Stainton from Gangtok of a species of Mucuna with pale yellow flowers. In this publication she remarks that Stainton’s collection is possibly a colour variant of M. macrocarpa lacking the purple wings. M. laticifera described here is fairly common in and around forests of Gangtok and exhibits pale yellow flowers as observed by Stainton in his Gangtok collection. We therefore believe that Stainton’s collection probably represents M. laticifera and not M. macrocarpa which is generally distributed at lower elevations and exhibits bicoloured corolla.

Figures

FIGURE 1. Mucuna laticifera A–Leaf, B–Inflorescence, C–Bracts, D–Flower, E–Calyx, F–Standard, G–Wing, H–Keel, I–Staminal tube, J and K–Stamens, L–stipitate gland, M–Gynoecium, N–Enlarged portion of stigma, O–pod with hairs, P–Seeds. All from Swaroopsingh 040. Illustration by Swaroopsingh Gaikwad.

FIGURE 2. Mucuna laticifera A. Habit with mature leaves and flowers. B. Inflorescence. C. Flower at anthesis. D. Fruit and seeds. Photographs by Navendu Page.