AMORPHOPHALLUS OPERCULATUS
PROTOLOGUE: Amorphophallus operculatus Hett. & Sizemore, published in Aroideana 26: 113 (2003).
Amorphophallus operculatus Hett. & Sizemore sp. nov. Ab Amorphophallo saururus tubero multo tenuiore longioreque, spadice spatha aequilonga, antheris inferioribus operculatis differt. Type: Hetterscheid H.AM.994-T (L, spirit coll., holotype), THAILAND, Chumphon prov., Chumphon, coll. from a living plant in the Leiden Botanical Garden, 31 July 2003 (orig. coll. M. Sizemore s.n.).
DISTRIBUTION: Pen. Thailand: Thailand.
DISTRIBUTION NOTE: Thailand: Chumphon Province, where the type plant was collected.².
SPECIES DESCRIPTION:
Tuber elongate, thin, vertically rhizomatous, branching, to 40 cm long, 1-4 cm in diam. at the top; petiole 10-65 cm long, 0.4-1.5 cm in diam., smooth, uniformly olive green to dark rich reddish green, sometimes with a few small, dark spots near the base; lamina moderately or highly dissected, 20-70 cm in diam., rachises winged throughout; leaflets elongate ovate to ovate-lanceolate, top acute-acuminate, 2-14 cm long, 1-5 cm in diam., fleshy, upper surface a rich dark emerald green, margin reddish, lower surface dark greyish green, often flushed dark purple-violet, rachises on the lower side rich dark reddish purple.²
INFLORESCENCE:
Peduncle 33-50 cm long, 6-8 mm in diam., smooth, dull reddish mauve with or without a few darker, irregular indistinct spots at the base. Spathe broadly triangular-elliptic, 8-12 cm long, 6-11 cm in diam., margins concave, base and limb hardly separated, base convolute, ca. half the length of the spathe, not opening to the base during male anthesis, top acute, outside whitish changing to pale dirty greyish-white near the base, veins pale pinkish, upper half suffused with a pale pinkish-purplish hue, inside dirty whitish, top with a pinkish-purplish hue, base within densely clothed with mostly more or less globose verrucae, those on the dorsal side and close to the spadix base elongate and/or slightly rugate, the entire inner surface of the base covered with a wet film. Spadix sessile, longer than spathe, 10-14.5 cm long; female zone cylindric, 0.8-1 cm long, 0.8-1.1 cm in diam., flowers congested; male zone elongate, slightly conical, base constricted, top slightly or more distinctly laterally compressed, 3.5-4.8 cm long, 0.8-1.4 cm in diam. at the base, 0.5-1.2 cm in diam. at the top, flowers congested; appendix elongate conical, thin-walled, 5-8.2 cm long, 0.9-1.5 cm in diam. at the base, terete or slightly laterally compressed, more distinctly near the base, top acute, surface slightly and shallowly rugose, off-white. Ovaries subglobose, 2 mm in diam., 1.8-2 mm long, pale green, unilocular; style elongate conical, 0.8-1.1 mm long, 0.8 mm in diam. at the base, 0.5 mm at the top, pale purple or pale green flushed pale purple; stigma depressed, 1-1.2 mm in diam., ca. 0.5 mm high, with a shallow irregular central depression, surface verruculate, off-white. Male flowers having mostly 4-5 stamens, the lower flowers with only 1-2 stamens; stamens 1-1.2 mm long, 0.8-1 mm in diam.; filaments ca. 0.5 mm long, connate, whitish; anthers 0.5-0.7 mm long, truncate, pores apical, slightly elongate, those of the more isolated lower anthers lunate to entirely ring-like around the upper rim of the anther, the anther then seemingly operculate.²
PROPAGATION:
Results with this species ranged from 96.1% with early August cuttings to 2.1% with mid-October cuttings. With proper timing, this was among the species that rooted at the highest percentages in the trials.
ETYMOLOGY:
From Latin operculatus, “lidded”: the epithet refers to the peculiar shape of the pores of some of the lower male flowers, whose openings run round the upper rim of the anther as a crescent or a complete ring, so that the anther appears to be closed by a lid.²
NOTES:
1. Diagnosis: it differs from Amorphophallus saururus in the much thinner and longer tuber, the spadix equalling the spathe, and the operculate lower anthers.²
2. Amorphophallus operculatus belongs to a small group of species so far known only from Thailand, recognised by elongate, branching tubers, very dark velvety green leaves with thin purplish-red margins, and whitish spathes with concave margins. The other members are Amorphophallus saururus, Amorphophallus pygmaeus, Amorphophallus sizemoreae and Amorphophallus vogelianus. From all of them it differs in its very long, thin tuber - short and thick in the others - and in the operculate lower male flowers, which none of the other four possesses.²
3. The inner surface of the spathe base is covered with a wet film at anthesis, and the spathe does not open all the way down to the base while the male flowers are shedding pollen.²
REFERENCES:
1. Plants of the World Online, Royal Botanic Gardens, Kew — Amorphophallus operculatus Hett. & Sizemore
2. Aroideana 26: 113 (2003) — protologue.
3. Alan Galloway — Amorphophallus operculatus, alangallowaybotanicals.com.
4. Propagation of Amorphophallus by Leaf Petiole Cuttings — Juniper Level Botanic Garden
Additional photos by Robert Wainblat