AMORPHOPHALLUS SINUATUS

PROTOLOGUE: Amorphophallus sinuatus Hett. & V.D.Nguyen, published in Aroideana 26: 115 (2003).

2. Amorphophallus sinuatus Hett. & Nguyen V.D., sp. nov. Type: Hetterscheid H.AM.1154-T (L, spiritcoll., holotype), VIETNAM, Quang Binh province, Bo Trach distr., Son Trach commune, Phong Nha (coll. from a living plant cultivated in the Leiden Botanical Garden, 25 April 2003, orig. coll. Nguyen V.D. 185 p.p. as for the tuber sent to the Leiden Bot. Garden, coll. on 31 March 1997, “at the foot of a limestone mountain, in forest shade, alt. ca. 50-100 m”). Diagnosis - Ab Amorphophallo subpedato appendicis diametro eo zonae masculae aequali, stigmate distincte maiore ovarium fere tegenti, folio non subpedato differt.

DISTRIBUTION: Vietnam: Vietnam.

DISTRIBUTION NOTE: Vietnam: Quang Binh province, in the Son Trach commune of the Bo Trach district, at Phong Nha - the only area known.².

SPECIES DESCRIPTION:

Tuber elongate, to 20 cm long and 2-3 cm across at the top, tapering to the base, not branching. Petiole 17 cm long and 4 mm across, uniformly pale green. Lamina 45 cm across, the rachises unwinged; leaflets elongate elliptic, 19 cm long and 7 cm across, acuminate, the upper surface dull green and the lower surface glossy green.²

INFLORESCENCE:

Peduncle smooth and pale green throughout, 10 cm long and 0.5 cm across, almost entirely hidden by the longest cataphyll. Spathe broadly triangular, 3 cm long and 3.5 cm across, the limb and base not differentiated, the top obtuse, outside uniformly pale green with slightly darker veins, inside as outside but slightly paler and with a slightly darker base, the base within bearing scattered shallow whitish-greenish dot-like warts. Spadix sessile and distinctly longer than the spathe, the male part reaching well beyond it, 11 cm long; female zone cylindric, 1 cm long and 0.8 cm across, the flowers congested or slightly apart; male zone cylindric, 4 cm long and 0.7 cm across, the flowers congested and the lower ones slightly apart, adjacent flowers in the same spiral sometimes fused, and in the upper part of the zone the individual flowers scarcely recognisable except as separate stamens; appendix elongate cylindric-conical, 6 cm long, 0.8 cm across at the base and 0.4 cm near the top, tapering, slightly flattened front to back, smooth, very pale green, the top more or less obtuse, giving off a powerful stench of oligomethyl-oligosulphides. Ovaries obconical with a strongly truncate top and the base sunk into the axis of the spadix, 2 mm across and 1 mm high, bright pale green, one-chambered; style thick and short, 0.2-0.4 mm long and 0.8 mm across, pale green; stigma large and depressed, shallowly three-lobed with broadly obtuse lobes, 1.5 mm across and 0.8 mm high, the surface scabrate, white. Male flowers of 3-6 stamens, not counting the laterally fused ones; stamens 1 mm high and 0.8-1.2 mm across, rectangular or irregularly angular seen from above, truncate; filaments 0.5 mm long, fused, off-white; anthers 0.5 mm long, off-white, the pores of the thecae opening into a single central pore at anthesis by rupturing the connective, which is drawn out into a short cone.²

ECOLOGY:

The tuber the type was raised from came from the foot of a limestone mountain, in forest shade, at about 50-100 m.²

ETYMOLOGY:

From Latin sinuatus, “wavy-edged.” The epithet records the shape of the stigmas, which are large, shallowly three-lobed and almost wide enough to cover the ovary beneath them.²

NOTES:

1. The species is closest to Amorphophallus subpedatus, with which it shares the general build of the inflorescence, the mechanism of pollen release and a very short spathe. It differs in an almost cylindric spadix, distinctly larger stigmas, and a leaf that lacks the subpedate architecture of that species.²

2. The inflorescence also resembles that of Amorphophallus dzui, but there is no zone of staminodes.²

3. The anthers do not open by their own pores. At anthesis the pores of the two thecae break through into a single central opening, rupturing the connective, which is itself drawn out into a short cone.²

4. The spathe is only 3 cm long while the spadix is 11 cm, so the male zone stands well clear of it.²

5. The scent is a powerful stench of oligomethyl-oligosulphides.²

6. It comes from the same limestone country in Quang Binh as Amorphophallus tuberculatus.²

REFERENCES:

1. Plants of the World Online, Royal Botanic Gardens, Kew — Amorphophallus sinuatus Hett. & V.D.Nguyen

2. Aroideana 26: 115 (2003) — protologue.

3. Alan Galloway — Amorphophallus sinuatus, alangallowaybotanicals.com.