THAI FOREST BULLETIN

ARIOpSIS (ARACEAE: COLOCASIEAE) A NEW GENERIC RECORD FOR THAILAND & pRELIMINARY OBSERVATIONS
ON TRANS-HIMALAYAN BIOGEOGRApHY IN ARACEAE (p.C. BOYCE)
veins pinnate, radiating from petiole insertion, forming submarginal collective vein,
marginal vein also present, higher order venation reticulate. Inflorescence 1–3 in each
floral sympodium, appearing before or with leaves. peduncle very slender, equalling to
much longer than spathe, erect to spreading. Spathe ovate, boat-shaped, fornicate, not
constricted, gaping widely, not convolute at base, marcescent. Spadix shorter than spathe;
female flower zone adnate to spathe, very short and few-flowered, sometimes separated
from male zone by short, free, naked axis; male flower zone fertile to apex, relatively
thick, cylindric-conoid, many-flowered. Flowers unisexual, perigone absent. Female
flower an ovoid to ovoid-oblong ovary, 1-locular, ovules many, orthotropous, placentae
4–6, parietal, extending from base to apex of locule, stylar region absent, stigma stellate
with 4- to 6-laciniate lobes, lobes initially erect, later spreading and reflexed. Male flower
a peltate synandrium, connate filaments forming a stipe longer and narrower than dilated
common connective, thecae subglobose to ellipsoid, dehiscing by oval pore, synandria
all connate apically, forming a continuous surface punctured by cavities with somewhat
prominent margins into which pollen is shed from the 6(–8) surrounding thecae (each pair
of thecae belonging to a different synandrium). Fruit a 4–6-angled berry, stigma persistent,
many-seeded. Seed oblong, apically narrowed and obtuse, with indistinct strophiole, testa
thickish, longitudinally costate, embryo axile, small, endosperm copious.
Distribution.— 2 species distributed with one in Western India (A. peltata) and the
other (A. protanthera) in the tropical & subtropical eastern Himalayas through northern
Burma to northern Thailand. Fig. 1.
Ariopsis protanthera N.E.Br., Rep. Roy. Bot. Gard. Kew 1877: 51. 1877. Hook.f., Fl.
Brit. India 6: 519. 1893; Mayo et al., Gen. Araceae 275, pl. 99 & 129B, 1997.— Ariopsis
peltata f. protanthera (N.E.Br.) Engl. & K.Krause in H.G.A.Engler, Pflanzenr. 4. 23E:
130. 1920. Fig. 2.
Very small, slender, seasonally dormant, lithophytic herbs with milky latex, to 12
cm tall. Stem a ± subglobose tuber, ca 2 cm diam., mostly clustered, covered with fibrous
cataphyll remains. Leaves solitary. petiole very slender, 6–14 cm, sheath very short; lamina
peltate, cordate-ovate, 5–10 by 4–10 cm, membranaceous, pale green above, glaucous
below, posterior lobes short, fully fused; primary lateral veins pinnate radiating from
petiole insertion, forming submarginal collective vein; higher order venation reticulate.
Inflorescence 1–3 in each floral sympodium, appearing before the leaves. peduncle very
slender, 4–5 cm, much longer than spathe, erect to spreading. Spathe ovate, boat-shaped,
2–2.5 by 1 cm, not constricted, fornicate, gaping widely at anthesis, not convolute at base,
marcescent, dull yellow. Spadix shorter than spathe, ca 1.5 by 0.4 cm; female flower zone
adnate to spathe, ca 4 mm long, few-flowered; ovaries rhombic-ovoid to rhombic-ovoidoblong,
ca 3 by 4 mm, pale green speckled purple, stylar region very short, stigma stellate
with 4–6 lobes, lobes initially erect, later spreading and reflexed, whitish green; sterile
interstice free, naked, ca 3 mm long; male flower zone fertile to apex, cylindric-conoid,
ca 1 cm by 4 mm, many-flowered, dirty very pale yellow; synandria peltate, the connate
filaments forming a stipe longer and narrower than dilated common connective, synandria
all connate apically, forming continuous surface punctured by cavities with somewhat
prominent margins into which pollen is shed from the 6(–8) surrounding thecae of which
each pair of thecae belongs to a different synandrium. Fruit a 4–6-angled berry, ca 5 by 5
mm, pale green, stigma persistent.
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