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Malesian Euphorbiaceae Descriptions |
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van Welzen, P.C. & Forster, P.I. 2011. Picrodendraceae (formerly Euphorbiaceae s.l. subfam. Oldfieldioideae). In: Nooteboom, H.N. (ed.), Flora Malesiana ser. 1, 20: 4561.
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Kairothamnus Airy Shaw, Kew Bull. 34 (1980) 596; Kew Bull. Add. Ser. 8 (1980) 121; Stuppy, Syst. Morph. Anat. Samen biovul. Euphorb (1995) 170; G.L.Webster, Ann. Missouri Bot. Gard. 81 (1994) 59; Radcl.-Sm., Gen. Euphorbiacearum (2001) 96; Welzen & P.I.Forst. in Noot., Fl. Males. ser. 1, 20 (2011) 57; G.L.Webster in Kubitzki, Fam. Gen. Vasc. Pl. 11 (2014) 97. Type: Kairothamnus phyllanthoides (Airy Shaw) Airy Shaw.
Shrubs to trees, only plants with one sexe observed, but probably monoecious (Radcliffe-Smith, 2001). Indumentum mainly absent, simple hairs on ovary/fruit and staminate disc. Stipules early caducous, minute. Leaves alternate, simple; petiole short, completely slightly pulvinate, transversely cracked when dry; blade with entire margin, caudate, penninerved. Inflorescences axillary fascicles, either with groups of staminate flowers or 1 or 2 pistillate flowers; bracts minute. Flowers pedicellate, actinomorphic, petals lacking, cream to white. Staminate flowers: sepals 4, free, imbricate, in 2 sizes; disc (or receptacle) flat, covering receptacle with holes for stamens, hairy; stamens 1014, free, anthers basi-dorsifixed, 2-thecate, thecae parallel, opening latro-extrorse with lengthwise slits; pistillode very small, pyramidal, up to 0.2 mm high. Pistillate flowers: pedicel elongating in fruit; sepals in 2 differently shaped whorls of 3, imbricate; disc lobes 3, somewhat club-shaped, opposite outer sepals, glabrous; ovary 3-locular, densely sericeous; ovules two per locule; style absent, stigmas erect, spade-like, adaxial surface stigmatic. Fruits capsular, dehiscing septicidally and (partly) loculicidally, brown; pedicel elongating up to 7.7 cm, thickening towards apex; wall woody when dry, less than 1 mm thick, glabrescent outside, glabrous inside, exocarp separating from meso- and endocarp via fibrous layer; columella slender, T-shaped, with fibrous covering. Seeds bean-like but triangular in transverse section, exotesta shiny, smooth, without fleshy layer or appendages.
Distribution See under species.
Classification Webster (1994) and Radcliffe-Smith (2001) place Kariothamnus in the subfam. Oldfieoldioideae (= Family Picrodendraceae), tribe Caletieae, subtribe Pseudanthinae. This equals the seed anatomical Micrantheum group of Stuppy (1995). However, the leaves are remniscent of the genus Phyllanthus (see species epithet) and the crackings in the petiole of dried specimens resemble Cleistanthus. However, pollen and seed resemble that of Austrobuxus (Oldfieldioideae).
Kairothamnus phyllanthoides (Airy Shaw) Airy Shaw, Kew Bull. 34 (1980) 596; Kew Bull. Add. Ser. 8 (1980) 21, plate 1: fig. 1; Welzen & P.I.Forst. in Noot., Fl. Males. ser. 1, 20 (2011) 57, fig. 4. Austrobuxus phyllanthoides Airy Shaw, Kew Bull. 29 (1974) 303. Type: NGF (R.J. Johns) 47324 (holo K; iso L), Papua New Guinea, Morobe District, Morobe Subdistrict, Paiawa Valley, 7° 35 S, 147° 15 E.
Shrubs to medium-sized trees, up to 15 m high, bole up to 5 m high, dbh up to 20 cm; branches drooping; flowering branches 0.81.3 mm thick, epidermis of older branchlets with longitudinal slits around pustular lenticels. Bark 68 mm thick; outer bark smooth to vertically fissured, peeling off in flakes, grey to grey-brown; middle bark green; inner greenish-deep red to deep red; wood hard and heavy, straw-coloured. Stipules triangular, 0.51.2 by 0.40.6 mm, symmetric to asymmetric. Leaves: petiole channelled above, 38 mm long; blade ovate, 3.38.7 by 1.24.9 cm, length/width ratio 1.72.2, symmetric, papyraceous, base broadly cuneate; margin somewhat revolute, apex caudate, tip rounded and mucronulate, both surfaces smooth, though often pustules present, yellowish green to dark green and generally glossy above, light green and duller beneath; venation slightly raised on both sides when dry, nerves 57 per side till apex, looped and closed near margin, veins and veinlets reticulate. Inflorescences: bracts c. 0.7 by 0.5 mm, apex erose. Staminate flowers c. 5 mm in diameter, very fragrant; pedicel 89.5 mm long, capillary, round; sepals: 2 smaller ovate, c. 1.8 by 1.5 mm, margin entire, 2 larger obovate, c. 2.7 by 2 mm, apex very broadly rounded and serrate; filaments 11.5 mm long, thick, round; anthers c. 0.6 by 0.5 mm. Pistillate flowers 4.55 mm in diameter; pedicel c. 1.5 cm long, round, broadening towards apex; sepals 6, in two whorls of 3, outer whorl elliptic, c. 5 by 1 mm, acute, apex recurved, inner spathulate, c. 4 by 2 mm, subcucullate, margin membranous, apex acute, black; disc lobes c. 0.3 mm high; ovary ovoid, c. 1.5 by 1.5 mm, stigmas with c. 0.5 mm high stipe and c. 1.3 by 1.1 mm blade-like part. Fruits (seen dehisced) ovoid to subglobose, up to 13 by 13 mm, green when young; pedicel elongating up to 7.7 cm; columella 78 mm long. Seeds elliptic, 8.48.5 by 44.2 by 3.53.8 mm.
Distribution Monotypic, endemic in Papua New Guinea, Morobe Prov. (Lae and Morobe Subprov.).
Habitat & Ecology Along river banks in advanced secondary forest; soil: one time recorded from ultrabasic soil. Altitude: sea level up to 70(200) m. Flowering: April, May, August; fruiting: April, May, June, August.
