AMORPHOPHALLUS ERYTHRORRHACHIS

PROTOLOGUE: Amorphophallus erythrorrhachis Hett., Pronk & R.Kaufmann, published in Aroideana 29: 50 (2006).

Amorphophallus erythrorrhachis Hett., O. Pronk & R. Kaufmann sp. nov.

Amorphophallo taurostigma simillimus, valde spadice spatha aequilongo differt.

Type: from a plant cultivated by R. Kaufmann (orig. coll.: MADAGASCAR (NW). Beravina, Mahajanga Province, O. Pronk), 19 December 2004, Kaufmann s.n. (holotype, WAG, (spirit collection.).

DISTRIBUTION: W. Madagascar: Madagascar.

DISTRIBUTION NOTE: Beravina, Mahajanga Province.

SPECIES DESCRIPTION:

Tuber depressed-globose, to 25 cm in diam., offsetting behaviour unknown. Leaf solitary; petiole to ca. 100 cm long, to 4.5 cm in diam.; lamina strongly divided, to ca. 100 cm wide; rachises winged distal from the basal main branching point, wings green or bright carmine-red; leaflets elliptic to lanceolate, 1–20 cm long, 0.9–6.5 cm wide, narrowly acute or acuminate, upper surface all green or the basal part of the main vein bordered bright carmine-red.

INFLORESCENCE:

Inflorescence solitary; peduncle pale brown with numerous small whitish streaks and scattered rounded to elliptical blackish green spots or additionally with rounded or elliptical whitish-greenish spots and/or with pale brown spots with a blackish margin; spathe elliptic, 67 cm long, 28 cm wide, base obconical, not strongly separated from limb, limb expanded, upper half strongly helically twisted, outside a complex, dense pattern of dark green or pale greyish green rounded spots on a pale greyish olive-green background with numerous white punctiform spots, upwards with or without a dark brown hue, inside base deep or pale maroon, the rest ivory white towards the margin changing to pale brownish greenish with scattered, rounded blackish green spots, base inside strongly grooved-verrucate, apex acute. Spadix shorter than spathe, 45.5 cm long; female zone subcylindric, apex slightly expanded, 7.5 cm long, 3.5 cm in diam., flowers slightly distant; male zone subcylindric, base slightly constricted, 8 cm long, 2.8 cm in diam. at the base, 3.2 cm at the apex, flowers densely congested; appendix elongate conical, 30 cm long, 4 cm in diam., hollow, surface slightly grooved and rugulose, pale grey or pale greyish green, apex subacute to obtuse. Ovary ovate, 3 mm long, 3 mm in diam., bilocular, lower half bright pale green, upper half dull olive-green or dark purple, placentation basal; style cylindric, 2–2.3 mm long, 1 mm in diam., olive-green or dark purple; stigma depressed, obcordate in lateral view, deeply bilobed, 2.5 mm in diam., 1.5 mm high, lobes rounded, surface densely verrucate, dirty pale ochre. Male flowers consisting of (2–)3–5 stamens; stamens 2.5 mm long, 2 mm in diam.; filaments thick, 0.5 mm long, off white, free; anthers truncated, 2 mm long, off-white, pores apical, slit-like, connectives olive-green or maroon. Pollen psilate.

ECOLOGY:

Known from the seasonally dry region of western Madagascar, where the natural vegetation consists primarily of dry deciduous forest and woodland. The region experiences a pronounced dry season followed by summer rains. Much of the landscape around Beravina has subsequently been converted to wooded savanna and grassland. The precise microhabitat and substrate of the type collection were not recorded.

ETYMOLOGY:

The species epithet is derived from Greek erythros, “red,” and rhachis, “spine” or “rachis,” referring to the bright carmine-red rachises of the leaf blade. This character is, however, reported not to be present in all specimens of the species.

NOTES:

1. Amorphophallus erythrorrhachis shares many characters with Amorphophallus taurostigma but differs markedly in the spadix being considerably shorter than the spathe (the reverse in Amorphophallus taurostigma). This character is shared with Amorphophallus hildebrandtii Engl. & Gehrm. and Amorphophallus antsingyensis. From the former Amorphophallus erythrorrhachis differs in a much wider open spathe (almost cylindric in Amorphophallus hildebrandtii) and the much larger and differently shaped stigmas (conical and only 1 mm in diam. in Amorphophallus hildebrandtii) and the appendix being much more elongate (versus short-conical in Amorphophallus hildebrandtii). From the latter it differs in the much larger dimensions, different colours in most parts (versus almost all green in Amorphophallus antsingyensis) and the style being much longer (only 0.5 mm in Amorphophallus antsingyensis).

REFERENCES:

1. Plants of the World Online, Royal Botanic Gardens, Kew — Amorphophallus erythrorrhachis Hett., Pronk & R.Kaufmann

2. Aroideana 29: 50 (2006) — protologue.

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

Additional photos by Bjørn Malkmus-Hussein, Mathieu de Foucault and Cedric de Foucault