AMORPHOPHALLUS PUSILLUS

PROTOLOGUE: Amorphophallus pusillus Hett. & Serebryanyi, published in Blumea 39: 286 (1994).

Amorphophallus pusillus Hett. & Serebryanyi, spec. nov. A speciebus omnibus in tubere parvo elongate-ramoso, spathae basi connata semi-infossa differt. - Typus: Hetterscheid H.AM.247-T (L holo; spirit coll.), 11-i-1993, cult. Hort. Bot. Leiden ex Vietnam, Xuen Moc Reserve, easternmost part of Dong Nai Province (orig. coll. A. Kuznetsov, 1991).

DISTRIBUTION: Vietnam: Vietnam.

DISTRIBUTION NOTE: Vietnam: Dong Nai Province - the Xuyen Moc Reserve in the easternmost part of the province; known only from the type locality.².

SPECIES DESCRIPTION:

Tuber shortly napiform, slightly irregular, up to 3.5 cm long, c. 2 cm in diam., weighing c. 10 g, dirty white to pale brownish, producing small globose offsets. Leaf solitary; petiole up to c. 8 cm long, c. 3 mm in diam.; lamina up to c. 30 cm in diam., rhachises unwinged; leaflets 5, elliptic, acute-acuminate, up to c. 11 cm long, c. 5 cm in diam., upper surface moderately glossy dark or mid green, with or without round white spots, these most numerous and confluent near the midrib.²

INFLORESCENCE:

Inflorescence short peduncled, half buried; peduncle subterranean, 0.2-1.7 cm long, 1-2 mm in diam., white, smooth; spathe broadly triangular, tubular, 2-2.8 cm long, 2.5-3.2 cm in diam., acute-apiculate, limb poorly differentiated, shortly triangular, base truncate, the lower 0.5-0.8 cm connate and the remaining part convolute, outside pale pinkish with a pale brownish tinge and some scattered, larger, irregular blackish spots, these confluent near the margin and near the top, veins brownish, inside base pale violet, above it a narrow dark violet band, above that the colour as on the outside but slightly paler, base within smooth with slightly raised veins and a few scattered shallow elevations. Spadix sessile, longer than spathe, 4.4-5.7 cm long; female zone 3-4 mm long, c. 7 mm in diam. including the styles, flowers congested; male zone slightly conic or cylindric, 10-12 mm long, c. 4 mm in diam., flowers distant, the lower ones often staminodial, the axis between the flowers exposed, white, with a triangular purple-brown spot above each flower or only with scattered punctiform purple-brown spots; naked zone between the male and female zones c. 1 mm long, white; appendix elongate cylindric-conic, subacute, base constricted, 3.5-4.5 cm long, slightly curved, shallowly rugulose, greyish white or white, largely covered by numerous minute, elongate, confluent purple-brownish spots, producing a faint suffocating scent. Ovaries slightly depressed globose, 1.7 mm in diam., 1 mm high, unilocular with one basal anatropous ovule, base whitish, the remainder suffused with numerous tiny blackish purple or brownish purple spots, confluent near the top; style 1-2 mm long, c. 0.5 mm in diam., coloured as the ovary; stigma 1-3 mm in diam., c. 0.2 mm high, 1-5-lobed with a distinct central depression and radiating grooves separating the lobes, or cup-shaped with 3-7 marginal, more or less conic, spreading lobes, or sometimes the entire surface variously folded and nearly closed, directed towards the spathe, dirty yellowish brownish with a faint purple hue or dirty greyish whitish, surface minutely rugulose. Male flowers consisting of 1, rarely 2 or 3 stamens; stamens 1-1.3 mm long; filaments 0.1-0.3 mm long; anthers 0.9-1 mm long, c. 1 mm in diam., rectangular or butterfly-shaped in cross section, truncate, ivory-white but with an elongate zone of confluent tiny purplish brown spots between the pores, pores elongate, apical but sometimes extending laterally and sometimes confluent; staminodes, when present, more or less pyriform, 1-2.5 mm long, 0.5-1 mm in diam., single or paired, white with tiny purple-brownish spots. Pollen finely striate.²

ECOLOGY:

Found in dipterocarp forest on sand²

PROPAGATION:

Our only attempt with this species resulted in 40% rooting from cuttings taken in late August.

ETYMOLOGY:

From Latin pusillus, “very small” or “tiny,” referring to the exceptionally diminutive stature of the species. The 1996 revision described Amorphophallus pusillus as the smallest species then known in the genus, with a spathe only about 2–3 cm long and an inflorescence partly buried in the soil.

NOTES:

1. Diagnosis: it differs from all other species in the small, elongate-branched tuber and in the spathe, whose base is connate and half buried.²

2. Amorphophallus pusillus carries an unusual suite of characters together: minute dimensions, a leaf that is often variegated, a partly underground spathe, a connate spathe base - shared with Amorphophallus elliottii - an irregular, multilobed, variously folded stigma, shared with Amorphophallus harmandii, and male flowers with a single stamen.²

3. Its general likeness is to Amorphophallus harmandii of Cambodia, which differs in being larger, in a long peduncle, in a spathe entirely above ground with a convolute rather than connate base, in 2- or 3-locular ovaries, and in male flowers of 2 to 4 stamens.²

4. The appendix gives off a faint suffocating scent.²

REFERENCES:

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

2. Blumea 39: 286 (1994) — protologue.

3. Aroideana 19 (1996):P7 - 131

4. Propagation of Amorphophallus by Leaf Petiole Cuttings — Juniper Level Botanic Garden