AMORPHOPHALLUS ONGSAKULII

PROTOLOGUE: Amorphophallus ongsakulii Hett. & A.Galloway, published in Aroideana 29: 67 (2006).

Amorphophallus ongsakulii Hett. & A. Galloway sp. nov. Ab omnibus congeneribus cum tuberibus globosis in tubere minutissimo (tuber matura 2 cm diam. tantum), foliolis minimis (usque ad 11 mm longis) differt. Etiam inflorescentiae et folia maturata simultanei producens extans qui character in speciebus rhizomatis occurit et in solo species tuberose sed multo maiore, Amorphophallus tuberculatus infra descripsi. Type: from a plant cultivated by A. Galloway (orig. coll.: LAOS, Khammouane Province, in heavy shade in soil pockets on boulders, A. Ongsakul s.n.), 29 July 2004, Galloway ACA-1534-01-T (holotype, WAG, spirit collection).

DISTRIBUTION: C. Laos: Laos.

DISTRIBUTION NOTE: Laos: Khammouane Province - known only from the type locality.².

SPECIES DESCRIPTION:

Tuber globose, to 2 cm in diam., annually producing numerous (to ca. 15), fusiform offsets. Petiole 7-9 cm long, ca. 2 mm in diam., smooth, pale yellowish green to dirty greenish brown, with or without darker, thin stripes; lamina 13-16 cm in diam., rachises narrowly winged throughout; main segments highly dissected; leaflets very small, 3-11 mm long, 2-4 mm in diam., elliptic to lanceolate, apiculate, margin very finely, slightly irregularly serrate, upper surface dark green with distinct whitish midrib, lower surface paler.²

INFLORESCENCE:

Flowering shortly after leaf maturation, sometimes flowering up to four times consecutively, with ca. 3-4 weeks separating each flowering. Peduncle smooth, 16 cm long, 2 mm in diam., base whitish gradually changing to very pale yellowish-brown; spathe elongate ovate, 34 mm long, 14 mm wide, erect, base tubular, loosely convolute, outside greyish-green with parallel dark greyish veins, inside dark purple, strongly verrucose, limb basal half auriculate, upper half pressed against the appendix, apex acute, outside whitish with thin, pale green venation, slightly transparent. Spadix sessile, longer than spathe, 42 mm long, slightly curved forward; female part 2 mm long, 3 mm in diam., flowers slightly distant; male part elongate, slightly conical, 12 mm long, 3 mm in diam. at the base, 2 mm in diam. at the apex, flowers distant, less so in the upper part; appendix shortly stipitate (stipe 1 mm long, purple), 27 mm long, 2 mm in diam. at the base, 1 mm in diam. at the apex, narrowly elongate conical, base narrowed to the stipe, apex obtuse, surface smooth, pale yellowish-brown. Ovaries depressed, two-lobed, ca. 2 x 1 mm in diam., 0.8 mm high, base white, upper half pale purplish, bilocular, locules separated by two strong lateral constrictions of the ovary wall; style conical, 0.2 mm long, 0.4 mm in diam. at the base, pale green; stigma depressed, 0.8 mm in diam., 0.3 mm high, very shallowly bilobed, minutely echinate, pale green. Male flowers consisting of 2-3 stamens; stamens irregularly angulate in shape, truncate, 0.3-0.5 mm in diam., 0.2-0.3 mm high; filaments ca. 0.1 mm long, fused, whitish; anthers 0.1-0.4 mm high, reddish purple; pores apical, orbicular. Fruiting part more or less globose, berries crowded; berries ovate, truncate, ca. 6 mm in diam., ca. 4 mm long, deeply bilobed, contracted between the seed-containing locules, surface rugulose, pale green with whitish punctation, area around the style remnant dark greyish green, 2-seeded; seeds globose or subglobose, 2-3 mm in diam., greyish to dirty greenish.²

ECOLOGY:

Found in heavy shade, in soil pockets on boulders²

ETYMOLOGY:

Named after Annop Ongsakul of Thailand, who collected the first plants ever found of this species, for his friendship with the second author of the name and his extensive help on past field expeditions.²

NOTES:

1. Diagnosis: it differs from every other species of the genus with a globose tuber in the minute tuber - only 2 cm across when mature - and the very small leaflets, up to 11 mm long. It also produces inflorescences and mature leaves at the same time, a character otherwise found in the rhizomatous species and, among tuberous ones, only in the much larger Amorphophallus tuberculatus.²

2. Amorphophallus ongsakulii is unique for its very small leaf carrying a very high number of very small leaflets, which gives the whole leaf the look of a fern. Its tuber is the smallest of all known species with globose tubers, yet the number of annual offsets it makes is the highest of any Amorphophallus; and of all the species with long peduncles it is beyond doubt the smallest.²

3. Another remarkable feature is repeated flowering within one season - up to four times in succession, about three to four weeks apart. That had previously been known only in Amorphophallus polyanthus, where flowering usually precedes leaf development instead.²

4. Its relationship to any known alliance within the genus remains obscure. The deep rich green upper surface of the leaflets recalls the Amorphophallus pygmaeus group, but the comparison stops there.²

REFERENCES:

1. Plants of the World Online, Royal Botanic Gardens, Kew — Amorphophallus ongsakulii Hett. & A.Galloway

2. Aroideana 29: 67 (2006) — protologue.

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