AMORPHOPHALLUS UMBRINUS
PROTOLOGUE: Amorphophallus umbrinus A.Galloway, Luu, Malkm.-Huss., Prehsler & Claudel, published in Aroideana 42(1): 57 (2019).
Amorphophallus umbrinus A. Galloway, Luu, Malkm.-Huss., Prehsler & Claudel sp. nov. Type: from a plant cultivated by A. Galloway (orig. coll.: VIETNAM, Bình Thuận Province), 11 April 2015, Galloway AGA-2487-01-T (holotype, SGN, spirit collection).
DISTRIBUTION: Vietnam: Vietnam.
DISTRIBUTION NOTE: Vietnam: Bình Thuận Province, scattered throughout.².
SPECIES DESCRIPTION:
Tuber depressed globose, to 10 cm across and 7 cm high, brown, with small annular root scars that are prominent especially over the upper half, producing no offsets. Leaf solitary; petiole to 90 cm long and to 2.5 cm across at the base, smooth, green above and turning gradually brownish towards the base, with numerous dark dots 1-2 mm long and irregularly oval, often merging off-white blotches of varying size that give a lichen-like pattern. Lamina to 110 cm across, the rachises winged beyond the basal branches; leaflets elliptic, acuminate, up to 22 cm long and 8 cm across, mid-green above and pale green beneath.²
INFLORESCENCE:
Inflorescence solitary; peduncle 20-22 cm long and 1-1.25 cm across at the base, patterned like the petiole but darker, reddish-brown to olive. Spathe erect and boat-shaped without a constriction, 20 cm long and 6.5 cm wide, longer than the spadix but overlapping it only as high as the female zone, so that the male zone and the appendix stand exposed; outside brownish with short vertical off-white stripes 0.2-1.5 cm high and 2 mm across, irregularly shaped blotches to 1 cm high and 0.75 cm across, and small dark dots; inside the lower third dark rosy-cream, the upper part deep burgundy with small creamy spots 1-5 mm across, smooth. Spadix very shortly stalked, shorter than the spathe, to 13 cm long; female zone cylindric, 3 cm long and 1.6 cm across including the styles, the flowers somewhat apart to congested; no sterile zone between the female and male zones; male zone conical, 6 cm long and 1.8-2 cm across, the flowers congested; appendix conical, to 3.5 cm long and 1.5 cm across at the base, the top obtuse, its staminodes not perfectly fused and separated by irregular shallow furrows, creamy-white. Ovaries depressed, circular in cross section, about 2 mm high and 2.5 mm across, burgundy, bilocular; style about 1 mm long and 1 mm across, burgundy, pointing slightly upwards; stigma roundish to oval, about 1 mm high and 2.5 mm across, mostly with a central depression, the surface weakly papillate, rosy-cream - and sometimes two stigmas fuse, the result irregularly and weakly two- or three-lobed and larger than a single one. Stamens about 2 mm long, creamy-white; filaments about 1.8 mm long, connate; anthers about 1 mm across; pollen creamy.²
ECOLOGY:
Found scattered through its province in a range of habitats, from hilly ground in filtered light to moist shaded soil beside streams.²
ETYMOLOGY:
From Latin umbrinus, “umber, earth-brown.” The epithet is for the dark earth-brown colouring of the inside of the spathe.²
NOTES:
1. It belongs to the Paeoniifolius-Manta clade, in the group holding Amorphophallus paeoniifolius, Amorphophallus bangkokensis, Amorphophallus prainii, Amorphophallus opertus, Amorphophallus scaber and Amorphophallus koratensis. These share a leaf of similar build, and most carry lichen-like patterning on the petiole.²
2. Its own petiole pattern is nearest that of Amorphophallus prainii, resembling colonies of lichen, while the colour and pattern outside the spathe are nearer the petiole of Amorphophallus koratensis.²
3. Its closest relative appears to be Amorphophallus opertus, with which it shares a shallowly to deeply furrowed appendix and entire stigmas. It differs from that species and from all the others in a distinctly stalked inflorescence and a much more slender, open spathe that leaves both the male zone and the appendix visible, and in a smooth rather than rough or slightly warted petiole.²
4. Two adjacent stigmas sometimes fuse into one larger, irregularly lobed body.²
REFERENCES:
1. Plants of the World Online, Royal Botanic Gardens, Kew — Amorphophallus umbrinus A.Galloway, Luu, Malkm.-Huss., Prehsler & Claudel
2. Aroideana 42(1): 57 (2019) — protologue.
3. Alan Galloway — Amorphophallus umbrinus, alangallowaybotanicals.com.