Mimosa leiocephala

  • Title

    Mimosa leiocephala

  • Authors

    Rupert C. Barneby

  • Scientific Name

    Mimosa leiocephala Benth.

  • Description

    231. Mimosa leiocephala Bentham, J. Bot. (Hooker) 4: 404. 1842.—"Goyaz, Gardner, n. 3706."—Holotypus, collected at Natividade, lat. 11°30'S, in I or II. 1840 (fl), K (hb. Hook.)! = NY Negs. 1907, 11653; isotypi, +B = F Neg. 1388! BM! G! P! W!

    M. leiocephala sensu Bentham, 1875: 439, 1876: 386.

    Erect shrubs attaining 2 m, the homotinous stems, lf-stks dorsally and axes of simple pseudoracemes of globose capitula thinly strigose with forwardly appressed, basally thickened setae to ±1-1.5 mm, the plane thick-textured lfts glabrous lustrous facially, minutely ciliolate, the inflorescence at anthesis efoliate and exserted but leafy in fruit. Stipules firm lanceolate ±4-7 x 1-1.5 mm, glabrous except for scant marginal setae, obscurely nerved, tardily deciduous. Leafstalks of major cauline lvs 4.5-10.5 cm, those approaching the inflorescence progressively or abruptly shorter, of uppermost lvs only 1.5-3 cm, the petiole including firm pulvinus 2—6 mm, the interpinnal segments (6-)8-10 mm; pinnae of primary lvs 5-15-, of uppermost lvs only 3-4-jug., subdecrescent proximally, the rachis of longer ones 3-4.5 cm, their interfoliolar segments to 1.5-2 mm; spicules 0; lfts of longer pinnae ±21-33-jug., the first pair ±0.5 mm distant from minute subulate paraphyllidia, the blades narrowly oblong obtuse or deltately subacute, the longer ones 3-5.2 x 0.8-1.4 mm, 3.5-4 times as long as wide, the subcentric midrib obscurely elevated dorsally, the ventral face veinless. Peduncles mostly geminate 1.5-2.5 cm; capitula without filaments 6-8 mm diam., prior to anthesis moriform; bracts oblanceolate 1.5-2.3 mm, glabrous except for minute random capitate cilia; flowers 4-merous 8-androus; calyx membranous turbinate-campanulate 0.6-0.7 mm, the low-deltate teeth at most 0.1 mm, tipped with a minute setula or glabrous; corolla narrowly funnelform glabrous ± 3 mm, the oblong-ovate cymbiform lobes ±1.4 x 0.8 mm, a little thickened and hooded at tip; filaments presumably pink, (?) free to base, exserted 4-10 mm. Pods sessile oblong, in profile 40-47 x 12-13 mm, the replum nearly 2 mm wide, produced into a subulate beak ±2 mm, the low-convex valves consisting of crustaceous endocarp ±0.1 mm thick and livid exocarp 0.5 mm thick, when ripe dark brown externally and like the replum strigose with forwardly appressed thick-based tapering setae ± 1 mm, separating entire from replum; seeds broadly compressed-ellipsoid, in wide profile 6-6.5 x 4.5 mm, the testa lustrous brown.

    In unrecorded habitat, but to be expected in cerrado near 500 m, known only from the environs of Natividade, on an e. affluent of rio Tocantins near 11°30'S, in n.-centr. Goiás, Brazil. -Fl. I—II(—?); fr. VI-VII.

    A modem collection of M. leiocephala from Natividade (Macedo 3842, NY) has shown that Bentham correctly foretold the nature of the pod, which closely resembles that of M. foliolosa sensu lato. In most other respects M. leiocephala simulates M. foliolosa var. foederalis, and can only be extracted from the orbit of M. foliolosa by virtue of the dorsally glabrous floral bracts and the perfectly glabrous corollas. The significance of this precarious difference, which up to the present appears correlated with dispersal, will need reappraisal as more is learned about the Pachycarpae of upland central Goiás.