AMORPHOPHALLUS TERRESTRIS

PROTOLOGUE: Amorphophallus terrestris Hett. & Claudel, published in Aroideana 35: 47 (2012).

Amorphophallus terrestris Hett. & C. Claudel, sp. nov. Type: EASTERN THAILAND, prov. Ubon Ratchatani, Hetterscheid H.AM.1568-T, coll. from a plant cultivated in the former botanical gardens of Wageningen University, 3 December 2007, orig. coll. C. Punpreuk s.n. (holotype, WAG, spirit coll.). Amorphophallus terrestris differs from Amorphophallus polyanthus by the stigma being two to three times larger, the style being at least twice as long, the appendix being half as long, the spathe lacking a strong constriction between base and limb, the tuber not flowering from more than one bud on the same main tuber, the scent being banana-like instead of fungal.

DISTRIBUTION: Thailand: Thailand.

DISTRIBUTION NOTE: Thailand: Ubon Ratchathani Province in the east of the country.².

SPECIES DESCRIPTION:

Tuber short elongate or elongate, sometimes narrowing towards the top, branching at the base or not, the top often carrying several apical buds of only partly separated daughter tubers; surface pale yellow and irregular, 6-9 cm long, 2.5-3.4 cm across at the top and 2-7 cm at the base. Petiole 10-30 cm long and 2-6 mm across, grooved, dirty dark olive green-greyish with indistinct slightly darker spots. Lamina with few leaflets, 20-50 cm across, the central main segment undivided and the lateral segments carrying 4-5 leaflets, the rachises narrowly winged beyond the basal branchings; leaflets elongate elliptic to oblong elliptic, 4-19 cm long and 2.5-7.5 cm wide, acute, the upper surface mid green with impressed venation, the lower surface pale green.²

INFLORESCENCE:

The inflorescences develop immediately after the leaf is shed - one from the apical bud, or that one accompanied by up to six more arising from lateral buds on the main tuber or from daughter tubers still undeveloped and not or only partly separated from it. Peduncle 1.5-2.5 cm long and 0.4 cm across, white, entirely underground. Spathe erect, 3.5-4.5 cm long and 3.5-4 cm across, only slightly narrowed between base and limb, the top acute; inside pale grey densely covered with minute brownish purple dots, the base maroon and paler near the insertion of the spadix; outside the limb as inside, the base dark maroon or purple below and uniformly grey above, smooth. Spadix longer than the spathe, 3.9-6.7 cm long; female zone 2-4 mm long and 5-9 mm across, the flowers slightly apart; male zone 8-10 mm long and 5-7 mm across, the flowers apart; appendix fusiform to obconic, more or less laterally flattened and often slightly to strongly fan-shaped or crested, 2.5-5.3 cm long and 6-8 mm across, obtuse or subacute, the surface smooth, dark grey or pale flesh-coloured, giving off a banana-like scent. Ovaries depressed globose, 2-3-lobed, 1 mm high and 2 mm across, irregularly warted, 2-3-locular, grey or white with purple spots; style thick, 0.4-0.6 mm long and as wide, grey or white with purple spots; stigma large, hemispheric or more or less strongly depressed with a central depression, or 2-3-lobed with one, 0.5-0.6 mm high and 0.7-1 mm across, the surface shallowly but densely warted, dirty yellow or off-white. Stamens of 1-3 anthers; filaments almost absent; anthers more or less subrectangular or subglobose, free or partly fused, 0.8 mm long and as wide, off-white, the connective deeply sunken, the pore apical and rounded. Infructescence globose, about 2 cm across, on a slightly lengthened peduncle. Fruit a dryish berry, 2-3-lobed and strongly constricted between the carpels, 2-3-seeded, dark grey with large pale pinkish spots that often run together, densely warted, with 1-3 lengthwise ridges and some scattered larger warts.²

ECOLOGY:

The whole inflorescence sits at ground level: the peduncle is entirely underground, and the berries ripen in about two weeks and detach easily from the axis.²

ETYMOLOGY:

From Latin terrestris, “of the ground.” The peduncle is wholly buried, so the spathe opens at the soil surface, and the berries fall to the ground beside the plant rather than being carried off.²

NOTES:

1. The species belongs to a group of six very small species with sessile inflorescences, together with Amorphophallus obscurus, Amorphophallus polyanthus, Amorphophallus pusillus, Amorphophallus serrulatus and one from Cambodia not yet described. Molecular work recovers the group with high confidence.²

2. Everything about the group points at animals living at the soil surface. The inflorescences sit on the ground, the sandy-coloured spathes may read as fungi, and the fruits are dry, soil-coloured and warted rather than the soft, brightly coloured berries the rest of the genus produces for birds.²

3. The scent is banana-like, and within the genus only Amorphophallus haematospadix smells the same way; in that species the compound responsible is isoamyl acetate. The fungal smell of Amorphophallus polyanthus, by contrast, comes from 2-heptanol.²

4. A second, unrelated group of small species arrives at the same end by another route: their infructescences are long-stalked and bend down to the soil as they ripen, setting the berries on the ground. Amorphophallus myosuroides and Amorphophallus ongsakulii are examples.²

5. The sister of the whole group is Amorphophallus sumawongii, a much larger plant of ordinary appearance and colouring - which nonetheless also has dryish fruits, green at full ripeness, with a warted and ridged skin.²

REFERENCES:

1. Plants of the World Online, Royal Botanic Gardens, Kew — Amorphophallus terrestris Hett. & Claudel

2. Aroideana 35: 47 (2012) — protologue.

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