Mimosa antrorsa

  • Title

    Mimosa antrorsa

  • Author(s)

    Rupert C. Barneby

  • Scientific Name

    Mimosa antrorsa Benth.

  • Description

    237. Mimosa antrorsa Bentham, J. Bot. (Hooker) 4: 403. 1842.—"Brazil, Pohl", the locality particularized in Martius, Fl. bras. 15(2): 384. 1876: "in provincia Minas Geraës ad Pedro Pereira [=Pedro Peiro, near Paracatú]."— Holotypus, Pohl d. 1426 = 2891, K! = NY Neg. 1903; isotypi, +B = F Neg. 1384! F! = F Neg. 54800, M! NY! US! W!-M. adversa Bentham, Trans. Linn. Soc. London 30: 439. 1875 & in Martius, 1876, l.c., nom. substitut. illegit. [Bentham considered the neo-Latin antrorsus, formed after the pattern of extrorsus, corrupt usage, but the Code makes no provision for rejecting such words, and antrorsus, meaning anteversus, here alluding to ascending aculei, has become respectable with time.]

    Shrubs and treelets 2-4 m with stiffly ascending, densely and amply leafy virgate branches, armed along prominent blunt cauline ribs and occasionally also along dorsal rib of some lf-stks with forwardly incurved, proximally puberulent aculei to (1-) 1.5-2.5 mm, except for glabrous upper (and at times lower) face of lfts minutely villosulous and also densely finely subappressed-setose overall, the setose element of the vesture lutescent, the pseudoracemose inflorescence of globose or plumpy ovoid capitula usually foliate proximally but distally exserted up to 1-2 dm from foliage. Stipules erect firm lanceolate ± involute 4-11 x 1.5-2 mm, densely setulose dorsally, thinly so within, deciduous with or before the associated lf. Leaf-stalks 4-15 cm, often progressively shorter distally along branches, the petiole including (or largely composed of) hard, densely appressed-setose pulvinus 4-11 mm, the longer interpinnal segments (4-) 5-10 mm; interpinnal spicules 0; pinnae 8-15(-17)-jug., decrescent proximally, the rachis of longer ones (2-)2.5-6.5(-8) cm, the longer interfoliolar segments 0.5-1 mm; lfts of longer pinnae 30- 55(-70)-jug., the proximal pair close to pulvinus (paraphyllidia 0), all linear-oblong, either acute or obtuse-apiculae, the longer ones 3.5-5.5 x 0.6-1 mm, the blades dark-olivaceous and veinless above, beneath paler and faintly 2-nerved from pulvinule. Peduncles solitary or distally geminate (12-) 15-30 mm; capitula without filaments 7.5-10 mm diam., prior to anthesis moriform, the obtuse, densely packed fl-buds densely setulose; bracts linear-spatulate or spatulate-oblanceolate 2.5-3 x 0.45-0.65 mm, beyond middle silky-setulose dorsally; flowers 4-merous 8-androus, the lower ones staminate, the lowest of all slightly smaller than the rest; calyx membranous campanulate 0.5-0.6 mm, the rim with setulae ± as long; corolla 3-3.8 mm, the glabrous tube funnelform, the ovate concave lobes 1.1-1.4 mm, hooded and callous-thickened at apex, densely silky-setulose dorsally; stamens alternately short and long, monadelphous through 0.45-0.75 around base of pilosulous ovary, the longer set exserted 4-5.5 mm. Pods 1-4 per capitulum, erect and long-persistent on stout ascending peduncle, in profile narrowly oblong or oblong-oblanceolate 33-55 x 8-12 mm, (7-)8-12-seeded, cuneately contracted at base into a stipe 2-7 mm, abruptly narrowed at apex into an erect cusp (1—)3—5 mm, the coarsely setulose replum 1.3-1.8 mm wide, the stiffly papery valves low-colliculate over each seed, externally densely strigose with appressed yellowish setulae, furfuraceous within, when ripe separating entire from replum except at very base, the dehiscence inert; seeds plumply obovoid ±5 x 3.5-4 mm, the smooth testa brown or livid.

    In cerrado and in bush islands in campo sujo or brejo, 800-950 m, discontinuously dispersed, mostly in stony soils, on both slopes of upper S. Francisco valley in Minas Gerais, from Grão Mogol w. through Sa. do Cabral to the sources of rio Paracatú, thence w. to head of rio S. Bartolomeu in Distrito Federal, Brazil.—Fl. XII-IV, the fruits persistent through the year.

    Mimosa antrorsa is readily known by the combination of prickly stems, small crowded leaflets, exserted pseudoracemes of capitula, and very densely strigose pods of tawny-yellow hue.