Heteroaridarum crassum (S.Y.Wong & P.C.Boyce) S.Y.Wong & P.C.Boyce

First published in Webbia 73: 51 (2018)
This species is accepted
The native range of this species is Borneo (Sarawak). It is a perennial and grows primarily in the wet tropical biome.

Descriptions

Extinction risk predictions for the world's flowering plants to support their conservation (2024). Bachman, S.P., Brown, M.J.M., Leão, T.C.C., Lughadha, E.N., Walker, B.E. https://nph.onlinelibrary.wiley.com/doi/full/10.1111/nph.19592

Conservation
Predicted extinction risk: threatened. Confidence: confident
[AERP]

CATE Araceae, 17 Dec 2011. araceae.e-monocot.org

General Description
Small, moderate to robust rheophytic herbs to ca. 20 cm tall. Stem epigeal, pleionanthic, erect to semi-decumbent, condensed, to 1.6 cm long x 1.3 cm diam., roots green, photosynthetic, robust to ca 2 mm diam. Leaves few together, spirally arranged, to ca 4 per module; petioles stout, glabrous, 4−8 cm long x 3.5−5 mm diam., dark green, similar colour to adaxial side of leaf lamina, D-shaped adaxially in cross section; sheathing only at the extreme base, the sheaths fused and extending into a very narrowly triangular marcescent ligular portion to ca 2.8 cm long, 1/3 to ½ of petiole length; lamina broadly oblanceolate to broadly oblong-lanceolate to elliptic or narrowly obovate, very stiffly coriaceous, glabrous, 11−14 cm long x 3−5 cm wide, base cuneate to decurrent, oblique, apex acuminate, sometimes acute, acuminate for ca 1.3 cm, tubular apiculate to ca 1.5 mm; margins entire, markedly thickened when fresh, revolute (in dry material), adaxially shining dark green, abaxially matte paler green, minutely rugulose, marked conspicuously with dense, raised punctate when fresh but weakly and minutely punctate in dry material; midrib adaxially flush with lamina, abaxially prominent, raised canaliculate in cross section; primary lateral venation weakly raised adaxially when fresh, 5-8 primary lateral veins at each side but obscure in dry material, very obscure abaxially when fresh and in dry material, secondary venation obscure, primary and secondary venation diverging at 30°-45° from mid-vein, running into obscure marginal vein; tertiary venation invisible.

Inflorescence solitary, sub-erect, sweet smelling (esterases) at female anthesis, peduncle to ca 8 cm long, always exceeding petioles, subtended by a pair of fused ligules, to ca 4.5 cm long these spliting into two at the end, to ca 2.3 cm long, sometimes two rudimentary leaves present, these to ca 2 mm followed by a prophyll and a cataphyll; spathe more or less broadly ovate, not constricted, softly coriaceous, interior glossy, exterior semi-glossy, to 6-8 cm long; lower spathe cup-shaped, obconic, 2.2 cm long x 1.9 cm diam. (across), spathe abcission layer coinciding with base of male zone, green
when fresh, persistent into fruiting, margins convolute; limb broadly ovate, convolute, white, to ca 3.8 cm long, tip mucronate to ca 3 mm, caducous after male anthesis; spadix sessile, adnate isodiametrically to the spathe in the lower ¼ of female zone on the dorsal side, cylindric, to ca 4.5−5.5 cm long, subequalling spathe; female zone cylindric, often constricted at the adnation, green when fresh, ca 1 cm long x 8.6 mm-1 cm diam., 1/5 of spadix length; pistils many, somewhat crowded, ovoid to elongate-ovoid, ca 1.2 mm long x 0.85 mm diam., turning white in alcohol, stigma sessile, raised, notably papillate, ca 0.60−1.1 mm diam., 2/3 of ovary diam., staining brownish red in alcohol; interpistillar staminodes, staminodes confined to a single row at the base of spadix, laxly arranged, more-or-less square to round, impressed in the middle, shorter than pistils, about same size as ovary, shortly stipitate; sterile interstice cylindric, always wider in diameter than female zone, 4−6 mm long x 8 mm−1.1 cm diam., 1/10 of spadix length, without constriction, clothed with staminodes, more-or-less circular, sometimes rectangular, truncate, ca to 1 mm across, excavation circular deep, sometimes wide impressed; male zone tapering-cylindric, basally slightly thickened above interstice, 2.2 cm long x 8 mm long, ½ of spadix length; stamens arranged in longitudinally aligned pairs, crowded, rectangular, ca 1 mm across; connective deeply excavated, with the cavity not septate; thecae opposite on the distal and proximal (with respect to the spadix axis) sides of the anther; horns very short, round to slightly point at end, erect to suberect; appendix tapering-cylindric to a blunt tip, ca 8.5 mm long, 1/5 of spadix length, staminodes more or less circular, sometimes irregularly polygonal, 0.6 mm to 1 mm wide, excavations circular deep, sometimes wide impressed. Infructescence solitary; peduncle to ca 8 cm long, not exserted, erect; fruiting spathe obconic, ca 2 cm.
Distribution
Endemic to Sarawak: Sri Aman Division (Gn. Gaharu).
Diagnostic
Aridarum crassum is clearly distinctive from the rest of the genus by the leaf laminae very stiffly coriaceous, glossy deep green adaxially and conspicuously raised punctate abaxially when fresh. Aridarum crassum is most similar to A. nicolsonii Bogner but is readily separable by the above noted characters plus in having stigmas smaller than ovary diameter, by inflorescences fragrant of esterases at female anthesis, and a taperingcylindric (vs cylindric) male zone. Additionally, A. crassum is more robust with stouter petioles than A. nicolsonii, which tends to be gracile with slender petioles.
[CATE]

Sources

  • Angiosperm Extinction Risk Predictions v1

    • Angiosperm Threat Predictions
    • http://creativecommons.org/licenses/by/4.0
  • CATE Araceae

    • Haigh, A., Clark, B., Reynolds, L., Mayo, S.J., Croat, T.B., Lay, L., Boyce, P.C., Mora, M., Bogner, J., Sellaro, M., Wong, S.Y., Kostelac, C., Grayum, M.H., Keating, R.C., Ruckert, G., Naylor, M.F. and Hay, A., CATE Araceae, 17 Dec 2011.
    • http://creativecommons.org/licenses/by-nc-sa/3.0
  • Kew Backbone Distributions

    • The International Plant Names Index and World Checklist of Vascular Plants 2025. Published on the Internet at http://www.ipni.org and https://powo.science.kew.org/
    • © Copyright 2023 World Checklist of Vascular Plants. http://creativecommons.org/licenses/by/3.0
  • Kew Names and Taxonomic Backbone

    • The International Plant Names Index and World Checklist of Vascular Plants 2025. Published on the Internet at http://www.ipni.org and https://powo.science.kew.org/
    • © Copyright 2023 International Plant Names Index and World Checklist of Vascular Plants. http://creativecommons.org/licenses/by/3.0