Homalomeneae (Araceae) of Borneo XXX — Homalomena atlas [Hanneae Complex] a new species from the Rejang Basin, Sarawak
From Firenze University Press Journal: Journal of Plant Taxonomy and Geography (Webbia)
Wong Sin Yeng, Institute of Biodiversity and Environmental Conservation, University Malaysia
Peter C. Boyce, Dipartimento di Biologia, Centro Studi Erbario Tropicale (herbarium FT), University of Florence
The Homalomena Hanneae Complex (Ng et al. 2011: 26) of the Cyrtocla-don Clade (Wong et al. 2013) is a highly distinctive group of species notable for leaf blades with conspicuous extrafloral nectaries, amber-coloured resin secreted from between the staminate florets shortly before staminate anthesis (Hoe et al. 2011, 2016; Wong & Boyce 2017), and spathes white at anthesis with the persistent post-anthesis spathe turning deep pink to red as the fruits develop. Until recognition of Homalomena electra P.C.Boyce & S.Y.Wong (Boyce & Wong 2017) from Peninsular Malaysia the Hanneae Complex was considered to be entirely Bornean (but see Wong et al. 2013: 592). Including that described here, the complex comprises 13 described species, all except H. electra restricted to Borneo, and with most species localized. Based on field observations and in particular the huge amount of undeterminable material deposited in herbaria the Hanneae Complex is most probably con-tains well in excess of 100 species Geology in this paper is specified based on Hutchinson (1989, 2005) and Tat e (2001).
Medium-sized, rather robust, evergreen, glabrous clumping herb to c. 1 m tall. Crushed tissues strongly aromatic of turpentine. Stem initially erect, decumbent with age with the active tip ascending, 3–3.5 cm thick, semi-glossy medium green; older parts brown; adventi-tious roots copious, conspicuous, penetrating petiole bases; internodes 1.5–2.5 cm long. Leaves up to ca 20; individual shoot modules beginning with a conspicu-ous 2-keeled semi-persistent scarlet prophyll; petiole 60–70 cm long × 9–12 mm wide, erect, older leaves with the petiole spreading or procumbent, pulvinate ca 2/3 way along from base, weakly D-shaped in cross-section with angles rounded, distally shallowly canaliculate with the angles bluntly rounded, medium green with broken paler longitudinal striae, lower fifth (about half equal to the length of the sheathing portion), glossy scarlet; peti-olar sheath 10–15 cm long, c. 1/5 of petiole length, with wings up to 1 cm wide proximally, tapering distally, open, weakly decurrent at apex, their margins slightly incurved; wings initially deep red brown, soon marces-cent along margin, eventually whole sheath marcescent; blade broadly ovato-sagittate or ovato-cordate, 35–45 cm long × 25–35 cm wide, thinly leathery; somewhat quilted between impressed primary veins, with scattered punctate extrafloral nectaries, semi-glossy dark green adaxially, slightly paler abaxially, sagittate at base with sinus narrowly triangular; posterior lobes subtriangular with the outer margin rather abruptly curved, and the inner margin straight to very slightly incurved, obtuse at apex; anterior lobe broadly triangular, acute; mid-rib raised abaxially, c. 8 mm wide at base, 4 mm wide at centre, adaxially impressed; primary lateral veins c. 20 on each side, diverging at 30–70° from midrib, adaxi-ally impressed, abaxially sharply raised, curved towards apex when near margin; interprimary veins slightly impressed adaxially, slightly raised abaxially, alternat-ing irregularly with primaries, posterior lobes each with 4–6 primary veins; secondary venation abaxially raised, arising from mid-rib and primary and interprimary veins; tertiary venation invisible, all veins running into a slightly thickened intramarginal vein. Blooms usually up to 10 together in a simple synflorescence, erect, smelling of anethole at anthesis, post-anthesis and into fruiting declinate; first bloom subtended by a red prophyll, c. 5 cm long × 1 cm wide; subsequent blooms subtended by slightly shorter red prophylls; peduncle 15–18 cm long × 5.0–7.5 mm wide, matte brick red with very numer-ous pale grey broken longitudinal striae.
DOI: https://doi.org/10.36253/jopt-14254
Read Full Text: https://oaj.fupress.net/index.php/webbia/article/view/14254
