Arisaema gracilentum Brugg., 2016

Bruggeman, P., 2016, Arisaema gracilentum, a new species of Arisaema (Araceae) from NE India, Blumea 61 (2), pp. 87-89 : 87-88

Arisaema gracilentum Brugg. , sp. nov. — Plate 1

Most closely similar to A. speciosum (Wall.) Mart. but differing in having a lanceolate, hooked spathe with a constricted spathe mouth, and dark purple-banded inner spathe blade. — Type: P. Bruggeman PBR485 (holotype CAL prepared from cult., paratype L, prepared from cult.), India, Arunachal Pradesh State, Lower Dibang District, Mayodia , on slope near road, 2200 m asl .

Etymology. The species epithet, from the Latin adjective gracilentus, literally ‘abounding in slenderness’ refers to the graceful appearance of the inflorescence.

Plant seasonally dormant, up to 70 cm tall. Subterranean stem short, rhizomatous, cylindrical to ovate, up to 7 cm long, 4 cm diam with numerous dormant offsets. Roots white, branching with short side roots. Aerial shoot absent or inconspicuous. Cataphylls 2 –3, up to 15 cm long, longest cataphyll often still enveloping the lower part of the inflorescence at anthesis. Leaf 1, blade often tinged purple underneath, dark green above. Petiole up to 70 cm long, up to 15 mm wide at base, 4–5 mm wide at the top, uniformly green, reddish, or minutely red-striated. Blade tri-foliolate, central leaflet broad elliptic, 20–30 cm long, 5–7 cm wide. Lateral leaflets elliptic-ovate, approximately equalling central leaflet, to 30 cm long, 6–8 cm wide, strongly asymmetrical. Inflorescence held below the leaf. Peduncle c. 10 cm long, green. Spathe tube pale green to green-beige tinged pink, sub-cylindrical to barrel-shaped, 5–6.5 cm long, 2.5–3 cm wide at base, narrowing to 1.5–2 cm below the mouth, spathe mouth constricted. Mouth margins revolute becoming strongly revolute along the midsection of the spathe blade. Spathe blade horizontal, lanceolate, ending in a sharp tip, green-beige outside with a broad dark purple band inside slightly fading towards the edge. Spadix unisexual. Male spadix 2.5 cm long. Male fertile zone 2 cm long and c. 8 mm across. Synandria densely arranged, pale pink-purple, 3–4-androus, thecae dehiscent by an elongated pore, pollen white. Female spadix fertile zone 3 cm long and 2.5 cm across. Pistils densely arranged. Ovaries ovoid, green striped purple, 2.0– 2.5 mm wide, stigma sessile, white. Spadix appendix sessile in male plants, sessile but with a slightly widened basal part in female plants, 100 cm long, exserted from the tube, base rugose, gradually tapering to a filiform thread.

Phenology — Flowering: April, May; fruiting: November – December.

Figures

Plate 1 Arisaema gracilentum Brugg. a. Inflorescence side view; b. plant in situ; c. inflorescence front view; d. male and female spadix; e. underground stem.