Homalomena prolixa
Herbs lithophytic, perennial, erect, to c. 20 cm tall, vegetative tissues strongly aromatic of celery. Stem pleionanthic, erect, highly congested, internodes to 0.5 cm long × c. 1 cm in diam. Modules subtended by a recurved 2-keeled prophyll c. 5 cm long × 1 cm wide. Leaves up to 15 together, spreading; petiole 10 – 12 cm long × c. 3 mm in diam. (terete portion of petiole distal to petiolar sheath), semi-glossy green with irregular darker streaks, basal dorsal portion (equivalent to ventral lowermost part of sheathing portion) of petiole slightly serrate-carinate; petiolar sheath wings spreading almost flat, 5 – 6.5 cm long × c. 1 cm wide, c. 1/2 length of petiole, wings long-persistent, rather membranous, slightly unequal, pale green with darker green veins; leaf blade broadly elliptic to somewhat ovate, 10 – 15 cm long × 5 – 6.5 cm wide, somewhat coriaceous, pale green abaxially, semi-matt dark green adaxially, base cuneate, apex acuminate and mucronate for c. 2 mm; midrib rounded-raised abaxially, particularly in portion of blade proximal to petiole, adaxially ± flush with blade, up to 3 mm wide; primary lateral veins c. 4 on each side, diverging at 35° from midrib, abaxially flush with and slightly darker than blade, adaxially flush with blade and scarcely differentiated; interprimary veins c. ½ width of primary lateral veins, irregularly interspersed between primaries, abaxially somewhat darker-pellucid and broken, adaxially flush with blade; secondary venation striate, almost invisible on both surfaces of blade; tertiary venation invisible; all veins running into a slightly thickened intramarginal vein. Inflorescences up to 6 together in a simple synflorescence, each subtended by a small narrowly triangular 2-keeled prophyll, erect at anthesis, later declinate; peduncle to c. 5 cm long × c. 3 mm in diam., expanding at insertion of spathe and there c. 5 mm wide, medium green. Spathe thinly stiff, with a distinct constriction between lower portion and spreading limb, tightly furled prior to anthesis, 6 – 7.5 cm long × c. 2 cm wide at anthesis, semi-glossy pale green externally, internally glossy greenish white; lower spathe broadly ovoid, c. 2.5 cm long × c. 2 cm in diam.; limb narrowly elliptic, somewhat hooded at anthesis, 4 – 5.5 cm long with a reflexed terminal mucro c. 10 mm long; lower spathe inflating and spathe limb gaping at pistillate anthesis, spathe limb opening wide at staminate anthesis and spadix extending and flexing at interstice to protrude from spathe; spathe later closing to re-enclose spadix. Spadix 5.5 – 6 cm long × c. 7 mm in diam., stipitate; stipe c. 2 mm long, pale green; pistillate flower zone weakly fusiform, c. 1/4 length of spadix, c. 2 cm long; pistils of lower 3/4 of zone quite crowded, upper 1/4 with spirals separated by flexing/extension of interstice, upper two spirals with pistils alternating with stout staminodes, pistils globose, c. 1.5 mm tall × c. 1 mm in diam., pale green, stigma capitate, wider than pistil, c. 1 mm tall × 1.5 mm in diam., semi-translucent, glossy greenish; interpistillar staminodes irregularly globose, on a slender stalk with an expanded top, ivory; sterile interstice c. 2.5 mm long post-extension, mostly naked, pale green, with c. 2 whorls of staminodes, those of lowermost whorl of similar structure to, but larger than (c. 2 mm in diam.), those associated with uppermost pistils, staminodes of uppermost whorl resembling staminate flowers, c. 2 mm in diam., ivory; staminate flower zone narrowly fusiform-cylindric, c. 3/4 length of spadix, exserted from lower spathe chamber, 3.5 – 5 cm long × 5 – 7 mm in diam., apex bluntly acute, yellowish ivory; staminate flowers mostly densely arranged, but lowermost 3 whorls slightly lax, trapezoid to sub-hexagonal in plan view, each flower consisting of 4 stamens. Infructescence with spathe remaining green. Fruits not observed.
Homalomena prolixa differs from all other described Homalomena species by the combination of open, spreading petiolar sheaths, leaf blades entirely lacking posterior lobes, a spathe with a marked constriction between the lower spathe and spathe limb, by the spadix extending and flexing in the region of the interstice with the lowermost whorls of staminate flowers individually separated, by the interpistillar staminodes present only in the upper two whorls of the pistillate flowers, and by the inflorescences smelling of lemon peel oil at anthesis. The celery-like smell of the vegetative tissues is also a new record for the genus.
Homalomena prolixa is to date known only from the type locality in SW Sarawak.
Homalomena prolixa occurs as a lithophyte on damp, shaded, vertical sandstone bluffs under moderately humid hill forest at an altitude of c. 130 m.