Vietnamocasia N.S.Lý, S.Y.Wong & P.C.Boyce, 2017

Ngoc-Sâm, Lý, Yeng, Wong Sin, Haevermans, Thomas, Dư, Nguy ễn Văn & Boyce, Peter C., 2017, Vietnamocasia, a new genus from Central Vietnam belonging to the AlocasiaColocasia clade (Araceae), Phytotaxa 303 (3), pp. 253-263 : 258

Vietnamocasia N.S.Lý, S.Y.Wong & P.C.Boyce , gen. nov.

— Type: Vietnamocasia dauae N.S.Lý, S. Y. Wong, T.Haevermans & D.V.Nguyen , sp. nov.

Vietnamocasia and its sole species Vietnamocasia dauae is a small to moderate terrestrial herb with elongated epigeal stems, watery white latex, a coriaceous peltate leaf blade lacking conspicuous waxy glands in the axils of the main veins of the abaxial surface, nodding inflorescences with a deciduous spathe limb and persistent lower spathe, a shortly stipitate spadix, a free pistillate flower zone, a staminate flower zone not enclosed by the lower spathe chamber spathe constriction, independent staminate flowers not aggregated into synandria and lacking an expanded synconnective, declinate infructescences, and single-seeded fruits. Vietnamocasia differs from all other genera of the Alocasia-Colocasia clade by independent staminate flowers not aggregated into synandria and lacking an expanded synconnective.

Small to moderate evergreen mesophytic herbs with irritant watery white sap; stems epigeal, elongated, initially erect, becoming decumbent in older plants, leafless portions with distinctive annulated scars, prophyll and cataphylls conspicuous during with flowering events, soon degrading and lost; leaves several together; petiole slender, spreading, green; leaf sheaths fully attached, persistent; leaf blade elliptic to oblong-elliptic, peltate, thickly coriaceous, glabrous, margin entire, adaxially glossy dark green, abaxially medium green, without waxy glands in the vein axils on lower leaf surface, anterior lobe with 5–6 sub-opposite primary lateral veins on each side; secondary venation conspicuous, not forming inter-primary collective veins; posterior lobes almost completely connate except for a shallow acute notch, tips divergent. Inflorescence nodding, usually 2–3 together interspersed with cataphylls; spathe constricted; spathe limb caducous; spadix distinctly shorter than spathe, shortly stipitate; pistillate zone free, cylindrical, many pistils; ovaries 1–locular; style very short; stigma discoid-subcapitate, inconspicuously three to four-lobed; sterile interstice subcylindric, gradually narrowed distally corresponding to the spathe constriction; lower synandrodia morphologically differentiated from the upper; staminate zone cylindrical, above constriction, slightly tapering distally; staminate flowers 2–3 androus, stamens free, oblong-linear, connective flat, conspicuous; appendix obvious, with more or less conspicuous brain-like patterning of longitudinal grooves. Infructescence declinate; fruits many, globose, single-seeded.

Etymology:— Vietnamocasia is compounded from the Greek classical name kolokasia, itself from an old Middle Eastern name qolqas ( Nicolson 1987) and the root of Alocasia and Leucocasia (and the more distantly related Colocasia ) + Vietnam.

Distribution:— Vietnamocasia is so far known only from the type locality and its vicinity.

Ecology:—At Mount Dầu V. dauae grows in moist shady understory of hillsides in secondary broadleaved forest dominated by dipterocarps at 150–490 m elevation.At the other known locality, Cà Đam, it occurs in primary evergreen broad-leaf forest at about 790 m elevation.