AMORPHOPHALLUS SERRULATUS

PROTOLOGUE: Amorphophallus serrulatus Hett. & A.Galloway, published in Aroideana 29: 75 (2006).

Amorphophallus serrulatus Hett. & A. Galloway sp. nov. Amorphophallus serrulatus species secunda folii margine vere serrulato gaudet. Species altera Amorphophallus smithsonianus est, quae tuberum subglobosum ac multos diversitates ceteros habet. Amorphophallus serrulatus Amorphophallo obscuro proximus, differt in laminae margine serrulato ut iam dixi, spatha constrictione una tantum, appendice multo breviore crassiore differt. Type: from a plant in cultivation by A. Galloway (orig. coll.: THAILAND, Tak Province, A. Galloway), Galloway ACA-1500-01-T (holotype, WAG, spirit collection).

DISTRIBUTION: N. Thailand: Thailand.

DISTRIBUTION NOTE: Thailand: Tak Province, the only locality known.².

SPECIES DESCRIPTION:

Tuber subglobose to slightly elongate, 1.5-2 cm long and 1-2 cm across, not branching. Petiole thin, 12-18 cm long and 0.3-0.5 cm across, smooth, uniformly pale green. Lamina subpedate and made up of only four to six leaflets, about 15 cm wide, the central main segment undivided and the lateral segments carrying two or three leaflets; leaflets elliptic to obovate, 6-8 cm long and 3.5-4.8 cm wide, the apex acute with a small mucronate tip, the margins minutely crenate-serrulate, the upper surface uniformly green or with a few small round white spots.²

INFLORESCENCE:

Peduncle 1 cm long and 3 mm across, entirely underground, smooth, white. Spathe erect, the convolute part slightly tapering to the apex, elliptic to elongate-elliptic, 2.5-3 cm long and about 2 cm across, outside pale pinkish or greyish with purplish veins, inside the base dark purple, the limb densely spotted whitish pink and dark purple or almost entirely dark purple, the apex acute, the upper margin of the limb often curved inwards and slightly rugulose on the outer surface, the base within smooth, long convolute, the basal part usually underground. Spadix longer than the spathe, sessile; female zone consisting of a single whorl of flowers, 1 mm long and 3 mm across, the flowers congested; male zone cylindric, 2.5-3 mm long and 3 mm across, the flowers congested or distant; appendix stalked, the stalk 0.5-1 mm long, the appendix itself fusiform, 1.8-2.5 cm long and 2 mm across at the middle, somewhat acute, the lower part smooth and whitish or spotted purple and white, the upper part rugulose and greyish, dirty creamish, or spotted purple and white. Ovary subglobose, more or less 2-lobed, laterally flattened, 1-1.5 mm across and 1 mm high, white spotted purple, bilocular; style oblique, elongate conical, 1 mm long, 0.5 mm across at the base and 0.2 mm at the irregularly lobed apex, dirty greyish-whitish; stigma 0.1-0.2 mm across, very thin, lateral, more or less cup-shaped and sunk into the apical tissue of the style, circular or oval with a central depression. Male flowers of 1-3 stamens; stamens 1-1.3 mm long; filaments about 0.3 mm long, connate; anthers 0.7-1 mm long and about 1 mm across, creamish. Pollen striate.²

ETYMOLOGY:

From Latin serrula, “a little saw”: the leaflet margins are finely toothed. Only one other species in the genus has a genuinely serrulate leaf margin - Amorphophallus smithsonianus - and the Latin diagnosis opens by saying so.²

NOTES:

1. The species belongs to the Amorphophallus pusillus alliance, a group of very small species with sessile inflorescences that molecular work has shown to hold together as a single lineage. Its other members are Amorphophallus pusillus, Amorphophallus obscurus and Amorphophallus polyanthus.²

2. Within that alliance it is told first by the toothed leaf margin, and then by a spathe constricted once rather than twice as in Amorphophallus obscurus, an appendix much shorter and thicker than that species has, an absence of staminodes unlike Amorphophallus pusillus, and a distinct style unlike Amorphophallus polyanthus.²

3. The whole plant is tiny. The tuber is 1.5-2 cm long, the spathe 2.5-3 cm, the peduncle 1 cm and entirely underground, and the female zone is a single ring of flowers.²

4. The stigma is not carried on top of the style but sunk into its side.²

REFERENCES:

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

2. Aroideana 29: 75 (2006) — protologue.

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