THAI FOREST BULLETIN (BOTANY) 36
or with a central hole, the upper ones resembling synandria; male flower zone cylindric, ca 3–7 cm long, ca 2 cm diam., whitish; synandria 5–9-merous, rhombohexagonal, convex- topped due to cap-forming synconnective, ca 2 mm diam.; appendix slightly thicker than the male zone at the base, thence tapering, equalling to considerably exceeding half the length of the spadix, yellowish. Fruiting spathe oblong-ellipsoid, ca 8 cm long, green. Fruits ellipsoid, ca 12 by 8 mm, ripening scarlet.
Thailand.— PENINSULAR: Phuket. See note below.
Distribution.— Indomalesia to Oceania. It is not clear where, if anywhere, this species occurs wild. It has evidently been prehistorically distributed widely in tropical Asia as a subsistence crop and is now pantropical by introduction as an ornamental
Ecology.— Roadside ditches, margins of wet fields, frequently cultivated as an ornamental in a number of selected forms; altitude: 0–500 m.
Vernacular.— None recorded. Uses.— Stems formerly used as a subsistence crop in times of famine.
Notes.— Together with Alocasia cucullata this is the commonest aroid in Thailand, yet there are almost no collections in herbaria, probably because being so common and also difficult to voucher it is routinely ignored by fieldworkers.
Alocasia macrorrhizos is never encountered in the wild but is always closely associated with human settlement. Arguably both Alocasia macrorrhizos and A.cucullata are cultigens.
A number of ornamental varieties have been recognised, which were discussed by Furtado (1941).
Alocasia navicularis (K.Koch & C.D.Bouche´) K.Koch & C.D.Bouche´, Index Seminum
1855(App.): 2. 1855. Hook.f., Fl. Brit. India 6: 524. 1893.— Colocasia navicularis K.Koch
& C.D.Bouche´, Index Seminum (B) 1853: 13: 1853.
Massive pachycaul evergreen herb to 1.5 m with milky latex. Stem erect to decumbent. Leaves several together, clustered at the tips of stems of larger plants. Petiole to 1.5 m long; petiolar sheath margins membranous; lamina peltate, cordato-ovate, 130 by 120 cm, apex short acuminate; primary lateral veins 9–12 on each side. Inflorescences 2–3 together among the leaf bases. Peduncle 40–45 cm, stout, much exceeding the cataphylls at anthesis. Spathe ca 10–20 cm long, constricted about 1/6th of the way from the base; lower part green, ovoid; limb broadly oblong-lanceolate, 18–15 by 4–8 cm, cowl-like at anthesis, dark yellow. Spadix shorter than the spathe, shortly stipitate; female flower zone 1–2 by ca 1.5 cm diam.; ovaries mid-green, ca 3 mm diam.; stigma sessile, 3–4-lobed, the lobes blunt, pale green. Sterile interstice equalling the male zone, ivory, narrowed corresponding to the spathe constriction; synandrodia rhombo-hexagonal, ca 2.5 mm diam., whitish, stained purple; male flower zone cylindric, ca 3–4 cm by 1.5 cm diam., white; synandria rhombo- hexagonal, convex-topped due to cap-forming synconnective, ca 1.5 mm diam.; appendix elongate-conic, 3–4 by 1–2 cm, equalling length of the spadix, about the same thickness as the male flower zone at the base, white. Fruiting spathe ellipsoid, ca 5–11 cm long. Fruits ellipsoid, ca 10 by 6 mm, ripening dark red.