Volume 11 > Part 2 > Year 2012 > Page 124 > Araceae > Alocasia

5. Alocasia hypoleuca P.C.Boyce

Thai Forest Bull., Bot. 36: 9. 2008. Plate XV.

Accepted Name : This is currently accepted.

Description : Very large to massive, pachycaul, evergreen herb to 3 m with clear latex. Stem erect to ca 2 m or more, slender and self-supporting, very seldom decumbent. Leaves several together, clustered at the tips of stems of larger plants; petioles to 0.75–1 m long, sheathing in lower ⅓–¼; leaf blade ovate-sagittate, bluntly triangular in general outline, held more or less erect, ca 100 by 50 cm, light green adaxially, conspicuously glaucous abaxially; primary lateral veins on each side of the anterior costa diverging at ca 60º; axillary glands of primary veins distinct; secondary venation flush with the blade, forming poorly defined interprimary collective veins; posterior lobes ca ⅓–½ the length of the anterior, somewhat rotund, naked in the sinus in adult plants, peltate in juveniles. Inflorescences paired among the leaf bases, subtended by membranous cataphylls; peduncle barely exceeding the cataphylls at anthesis; spathe ca 24–26 cm long, constricted about ¼ of the way from the base; lower spathe ovoid, glaucous yellow-green; spathe limb narrowly oblong-lanceolate, 20–22 cm long, hooded at anthesis, remaining hooded and then marcescent, pale green, conspicuously glaucous internally, less so externally; spadix slightly shorter than the spathe, weakly glaucous, sessile; pistillate flower zone ca 3 by 1.5 cm; ovaries globose, ca 2.5 mm diam., mid-green; stigma sessile, 3-lobed, the lobes blunt, deeply incised and erect, deep yellow; sterile interstice approximately twice the length of the pistillate flower zone, white, conspicuously narrowed corresponding to the spathe constriction; synandrodia elongated rhombo-hexagonal, ca 5 by 2 mm, the lower ones prismatic and not connate and thus staminodial, distinctly raised, proximally ivory and slightly glaucous, synandrodes on the main, narrowed part of the interstice white; staminate flower zone cylindrical, ca 8 by 1 cm, dirty whitish cream, slightly glaucous; synandria 3–5 androus, rhombo-hexagonal, synconnective flat, ca 1 by 2 mm; appendix less than the length of the spadix, very slightly thicker than the staminate zone at the base, then tapering, with conspicuous brain-like patterning of longitudinal grooves, pale cream. Fruiting spathe ovoid, ca 6–9 cm long, green. Fruit not seen.

Thailand : SOUTH-EASTERN: Chanthaburi (type: Boyce et al. 204, holotype -BKF).

Distribution : Endemic.

Ecology : Dry evergreen forests on granite; ca 500 m alt.

Notes: Alocasia hypoleuca is evidently closely related to A. macrorrhizos but readily distinguished by the very tall, slender, leafless stems that remain self supporting long after stems of similar length would be decumbent in A. macrorrhizos, the leaves conspicuously glaucous abaxially, the spathe limb internally and to an extent externally glaucous, the much more numerous and smaller synandria (ca 1 mm diam.) with flat (not convex) synconnectives, the proportionately shorter (less than spadix length) appendix and the deeply cleft, erect stigma lobes. The spathe is marcescent into fruiting (vs deliquescent).