Volume 11 > Part 2 > Year 2012 > Page 151 > Araceae > Amorphophallus

20. Amorphophallus fuscus Hett.

Aroideana 29: 55. 2006.

Accepted Name : This is currently accepted.

Description : Tuber depressed globose, 4–7 by 4–10 cm, offsets rhizomatous, to 15 by 1–1.5 cm, scaly. Leaf solitary; petiole 34–70 by 1–2 cm, smooth, mauve with dark brown to dark reddish brown, scattered, elongate oval or oval spots; leaf blade 52–80 cm, rachises winged above the basal branchings; leaflets elliptic to elliptic-lanceolate, 5–20 by 2–5 cm, broadly acuminate, with short apiculum, adaxially green, venation visibly highly reticulate. Inflorescence long-pedunculate; peduncle 15–20 cm by 7–9 mm, smooth, brown with scattered, elliptic very dark brown spots; spathe erect, ovate, 10–15 by 7–10 cm, base and limb not separated, shallowly convolute in the lower part, acute, exterior glossy brown, the lower part with very few, scattered, small, orbicular dark brown spots, upper part darker brown towards the margin, interior pale dirty yellow-green, the base dark maroon, with several very shallow warts; spadix sessile, as long as the spathe or slightly shorter, 10–13 cm long; pistillate flower zone cylindrical, ca 12 by 12 mm, flowers congested; ovaries 2–2.5 by 2 mm, 4–5-angular, apex hemispherical, base white, rest dirty purple, unilocular; style elongate conical, held almost parallel to the spadix, 1.5–2 by 1 mm at the base, 0.8 mm diam. at the middle, apex slightly expanded and shallowly lobed, pale green, base dirty purplish; stigma very thin, 0.3 by 1 mm, draped over the lobes of the style apex, radially 3–4-lobed-sinuate, shallowly verrucate, dirty pale greyish; staminate flower zone subcylindrical, ca 3 by 1.2 cm, slightly narrowing to the apex, flowers congested; staminate flowers 3–5-androus, off-white; appendix cylindrical-conical, base attenuate, apex rounded, 5.8–7.8 by 1.5–1.7 cm above the base, smooth, lower part with shallow, more or less diamond-shaped staminodes, diminishing upwards, surface off-white. Fruit not seen.

Thailand : N Thailand. Exact locality unknown (type: Musi s.n., cult. sub. Hetterscheid H.AM. 1294-T, holotype -WAG).

Distribution : Endemic.

Ecology : Limestone cliffs.

Notes: Amorphophallus fuscus shows a suite of characters that link it morphologically to such species as A. asterostigmatus (C Thailand), A. carneus (S Thailand & Malaysia), A. excentricus, (S Thailand) & A. krausei (Myanmar, N Thailand, SW China, Laos). This group has rather undifferentiated erect spathes, spadix as long as or shorter than the spathe and elongate conical appendices. The tubers are depressed-globose or subglobose and offsets are numerous, fusiform or rhizomatous. Amorphophallus fuscus differs from all these by the orientation of the style, the very thin small stigma and enlarged filaments in the lower staminate flowers. Furthermore it has a much denser reticulate higher order venation in the leaflets.

The typical style & stigma of Amorphophallus fuscus is found in Amorphophallus only in A. corrugatus(N Thailand, Myanmar, SW China) and A. kachinensis (same distribution) but both these species have near-globose appendices with strong convolutions or corrugation. The enlarged filaments of the lower flowers are found in the A. longituberosus-alliance, species of which have elongate tubers and produce a scent of anise from the inflorescence. The enlarged filaments probably serve as food rewards for the pollinators and are probably homologous to the staminodes in A. krausei and several other species.