AMORPHOPHALLUS RHIZOMATOSUS

PROTOLOGUE: Amorphophallus rhizomatosus Hett., published in Blumea 39: 273 (1994).

Amorphophallus rhizomatosus Hett., spec. nov. A speciebus omnibus in rhizomate tenui c. 1 cm crasso, appendice longissima myosuroide, spadice sessili differt. - Typus: Kerr 21104 (K holo, iso K), Laos, Muang Cha, Chiang Kwang, c. 1100 m, in evergreen forest on limestone, 17-iv-1932.

DISTRIBUTION: Indo-China: Laos, Vietnam.

DISTRIBUTION NOTE: Laos: Xiangkhouang - Muang Cha, at c. 1100 m, where the type was collected in 1932. Vietnam: Thua Thien-Hue Province.².

SPECIES DESCRIPTION:

Rhizome at least 20 cm long, c. 1.5 cm thick. Leaf solitary or paired; petiole slender, 29-57 cm long, c. 1 cm in diam. at the base, smooth; lamina 42-48 cm in diam., divided into only 5 or 6 large leaflets, rhachises unwinged; leaflets elliptic or elliptic-lanceolate, 14-20 cm long, 4-8 cm in diam., acuminate, base not decurrent, mid green above, pale green below.²

INFLORESCENCE:

Inflorescence occurring simultaneous with the leaf, long peduncled; peduncle slender, 40-53 cm long, c. 0.8 cm in diam., smooth, pale green; spathe oval, apex obtuse, 6-7 cm long, c. 5 cm in diam., outside base pale green shading upwards to whitish, base within smooth and purple. Spadix sessile, much longer than spathe, 16-17 cm long; female zone cylindric, 1-1.5 cm long, c. 0.6 cm in diam., flowers slightly or more distant; male zone elongate, slightly conic, 2-3 cm long, 0.6-0.8 cm in diam., upper limit sharp or diffuse, flowers congested or slightly distant; appendix myosuroid, acute, smooth, 12-13 cm long, 0.6-0.8 cm in diam. Ovaries more or less globose, c. 1.5 mm in diam., c. 1.5 mm high, green, unilocular; style poorly differentiated, c. 0.5 mm long, c. 1 mm in diam.; stigma flat, thin, entire or with a very shallow central depression, only slightly broader than the style, c. 1.2 mm in diam., c. 0.3 mm high, surface minutely verrucate, greenish yellow. Male flowers consisting of (2 or) 3 stamens; stamens 1 mm long, those in the lowermost flowers occasionally entirely connate within one flower to form a synandrium; filaments absent; anthers 1-2 mm in diam., truncate, pale yellow, connective brownish purple, pores apical, oval. Pollen irregularly striate.²

ECOLOGY:

Found in evergreen forest on limestone; altitude: c. 1100 m²

ETYMOLOGY:

From the Greek rhiza, “root,” by way of Latin rhizoma: the epithet describes the rhizomatous underground parts, which set the species apart from every other in the genus bar one.²

NOTES:

1. Diagnosis: it differs from all other species in the slender rhizome about 1 cm thick, a very long myosuroid appendix, and a sessile spadix.²

2. The rhizomatous underground part is shared only with Amorphophallus hayi, described in the same paper. Almost every other species in the genus grows from a tuber.²

REFERENCES:

1. Plants of the World Online, Royal Botanic Gardens, Kew — Amorphophallus rhizomatosus Hett.

2. Blumea 39: 273 (1994) — protologue.

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