Trichilia micropetala T.D. Penn., Fl. Neotrop.

Pennington, Terence D., 2016, Systematic Treatment Of American Trichilia (Meliaceae), Phytotaxa 259 (1), pp. 18-162 : 132-133

70. Trichilia micropetala T.D. Penn., Fl. Neotrop. 28: 172 (1981). Type:— BRAZIL. Amapá, Rio Araguari , fl., Pires, Rodrígues & Irvine 51334 (holotype, INPA; isotype, FHO, S). Map 79

Young shoots slender, 1–2 mm diam., puberulous at first (hairs basifixed), soon glabrous, becoming rough, brown, lenticellate. Bud scales absent. Leaves 2–3- foliolate or imparipinnate or pinnate with one of the terminal pair orientated to simulate a terminal leaflet, petiole 1–3.5 cm long, semiterete, puberulous at first; rhachis 2–3 cm long, semiterete; petiolule (0.5–) 2–4 mm long. Leaflets opposite to alternate, dimorphic, 2–5, with (1–)2 pairs of greatly reduced leaflets near the base of the petiole, 3.7 × 1.9–14 × 5 cm, elliptic to oblanceolate, apex acuminate, base narrowly attenuate, chartaceous; upper midrib sometimes puberulous, otherwise glabrous; glandular-punctate or -striate or not; venation eucamptodromous, midrib prominent on the upper surface; secondaries 8–11 pairs, ascending, arcuate and convergent; intersecondaries short or absent; tertiaries few, oblique to reticulate. Reduced basal leaflets 0.2–1.7 cm long, ovate, orbicular or reniform, petiolulate. Inflorescence axillary, 4.5–21 cm long, a laxly branched, slender thyrse, peduncle 2.5–5.5 cm long, lateral branches up to 4 cm long, sparsely puberulous or glabrous; pedicel 0.5–1 mm long. Flowers unisexual (plant dioecious). Calyx 0.5–1 mm long, patelliform, 4–5-lobed to halfway, sparsely puberulous outside or glabrous. Petals (3–)4(–5), fused for half to two thirds their length, valvate, remaining erect, male 1.75–2 mm long, female 2–2.5 mm long, ovate to lanceolate, minutely appressed puberulous outside, glabrous inside. Staminal tube cyathiform or urceolate, filaments completely fused, male 0.75–1.25 mm long and broad, female ca. 1.75 mm long, margin with 7–8 acute or subulate lobes alternating with the anthers and ½–2/3 their length, slightly bearded in the throat or glabrous; anthers 7–8, 0.4–0.8 mm long, glabrous; antherodes in female similar, without pollen and indehiscent. Nectary absent. Ovary ca. 0.5 mm long, ovoid, 3-locular, locules with 2 collateral ovules, puberulous; style minute, style-head capitate; pistillode smaller, containing minute abortive ovules. Capsule 2.2–3 cm long, 0.7–1 cm broad, 3-valved, narrowly ellipsoid, acute at apex and base, apex somewhat rostrate when dry, smooth, finely and densely appressed puberulous, pericarp 0.75–1 mm thick. Seed solitary, 2–2.3 cm long (including the apical arillode), ca. 0.4 cm broad; arillode developed along the adaxial surface and strongly developed at the apex and prolonged into a slender fleshy extension equalling the length of the embryo, abaxial surface of seed exposed; arillode also develops around the aborted ovules; seed coat membraneous. Embryo with plano-convex, collateral cotyledons, radicle apical, slightly exserted; endosperm absent.

MAP 79. Distribution of Trichilia micropetala T.D.Penn. Solid dots, distribution pre-1981, open dots new records 1981–2010.

Field Characters. Tree to 20 m high and 20 cm diam., bark dark brown, scaling in irregular plates, with some lenticels in vertical rows, slash ca. 3 mm thick, orange-brown. Flowers pale creamish-white, capsule greenish, the seed with a red or orange arillode. Flowering has been recorded in June, August, September, November and December, fruiting in April, September and October.

Distribution & Ecology. Southern Surinam to Amapá, Pará and central Amazonian Brazil in non-flooded rain forest, below 300 m elevation.

Additional Collections Examined. SURINAM. Sipaliwini, vicinity of Ulemari River (NW0254), Hammel & Koemar 21404 (K).

BRAZIL. Amapá: Rio Dois Irmãos, 12 km from Cupixi (NW0051), Rosa & Santos 1773 (MO). Amazonas: Manaus, Reserva Florestal Ducke (SW0259), Costa et al. 437 (K, NY), Sothers & Silva 674 (K). Pará: Tucurui (SW0349), Miranda et al. 351 (NY), 352 (NY), 686 (NY), Rosario 99 (NY), M.G. Silva & Rosario 5326 (NY).

Relationships. Now that the fruit is available for study, it is clear that this species is closest to T. surinamensis and T. cipo . Both these species share a similar floral, fruit and arillode morphology with T. micropetala . The latter differs from both in the presence of the greatly reduced basal leaflets, and fewer and usually smaller leaflets.