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THAI FOREST BULLETIN (BOTANY) 36

After anthesis all rots and falls but for the female part of the spadix and the lower spathe. As the fruits develop and expand, the peduncle generally elongates and the lower spathe enlarges, sometimes becoming conspicuously coloured (e.g., A. chaii P.C.Boyce). When the fruits ripen, the fruiting spathe dehisces to reveal orange to red fruits, analogous to arillate seeds in a capsule, contrasting with the discolorous lower spathe interior. The fruits are odourless as far as is known, fleshy and contain one to several seeds a few millimetres in diameter.

DISTINGUISHING ALOCASIA AND COLOCASIA

Traditionally, these two genera, which are undoubtedly closely allied and frequently confused with one another, have been separated on the basis of ovule number and placentation – many ovules on parietal placentas in Colocasia, few on basal placentas in Alocasia (e.g., Mayo, Bogner & Boyce, 1997: 90). These states are not really of practical use in field identification. However they translate in fruiting plants into markedly different dispersal syndromes, apparently (though not observed in West Malesia) involving birds in Alocasia, in marked contrast to the mammal dispersal syndrome of Colocasia where the fruits are smelly and inconspicuously coloured with many tiny seeds in slimy mucilage (see Hay, 1996).

In respect of synflorescence architecture, Alocasia may be readily distinguished from Colocasia by its bimodular synflorescence subunits. Inflorescence multiplication in Colocasia is achieved in such a way that the whole synflorescence is equivalent to one bimodular unit in Alocasia. Where the inflorescence terminating the vegetative module has only one further inflorescence in the axil of its subtending cataphyll in Alocasia (with the synflorescence being built up by relay axes), in Colocasia the second inflorescence has a third in the axil of its prophyll and so on up to c. 8 in Colocasia gigantea. The relay axis in Colocasia is vegetative and thus the whole synflorescence is displaced to a quasi-lateral position on one side of the shoot.

ALOCASIA

(Schott) G. Don in R.Sweet, Hort. Brit., ed. 3: 631 1839 nom. cons.; Hook.f., Fl. Brit. India 6:

  • 524.

    1893; Ridley, Fl. Malay Penins. 5: 97. 1925; Gagnepain in H.Lecomte, Fl. Indo-Chine 6:

  • 1142.

    1942; Mayo, Bogner & Boyce, Genera ofAraceae 283–286, Pl.104 i-iii & 130B, 1997;

Hay, Gardens Bull. Singapore 50: 221–334. 1998.— Ensolenanthe Schott, Bonplandia 9: 368. 1861 — Schizocasia Schott, Bonplandia 10: 148. 1862.— Xenophya Schott,Ann. Mus. Bot. Lugduno-Batavi 1: 124 1863.— Panzhuyuia Z.Y.Zhu, J. Sichuan Chinese Med. School 4(5): 49 1985.

Diminutive to medium-sized, rarely arborescent and gigantic, evergreen or rarely seasonally dormant monoecious herbs with clear to milky latex. Stem thick, often ± hypogeal, sometimes stoloniferous and tuberiferous, when epigeal then stem usually erect, rarely elongated and creeping. Leaves few to several in terminal crown, rarely solitary, sometimes each leaf subtended by a cataphyll. Petiole long, sometimes asperate or glandular, petiolar sheath relatively long, mostly persistent, sometimes deciduous. Lamina sometimes

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