Mimosa pogocephala

  • Title

    Mimosa pogocephala

  • Authors

    Rupert C. Barneby

  • Scientific Name

    Mimosa pogocephala Benth.

  • Description

    435. Mimosa pogocephala Bentham, J. Bot. (Hooker) 4: 382. 1841.—"Brazil, Sello", the data expanded in Martius, Fl. bras. 15(2): 333. 1876 to: "in provincia Minas Geraes."—Holotypus, Sello s.n., K (hb. Hook., fl, fr)!; presumed isotypi, +B = F Neg. 1357! G! K (hb. Benth., fl)! W!

    M. erinacea Bentham, J. Bot. (Hooker) 4: 383. 1841. — "Brazil, Sello; Morro Vermelho [s.-e. of Belo Horizonte, Minas Gerais], Langsdorff [properly Riedel, as corrected by Bentham, 1876: 333]."—Lectotypus, Riedel 642 (10), K!; isotypi, A! GH! US! = NY Neg. 11558\—Equated by Bentham, 1875: 403, with M. pogocephala.

    M. eriocaulis Bentham, J. Bot. (Hooker) 4: 383. 1841. — "Brazil, Pohl.", the data expanded in Martius, Fl. bras. 15(2): 333. 1876 to: "in Serra dos Pinheiros provinciae Goyaz . . . [conjecturally = Banderinha do Pinheiros s. of Queluz, Minas Gerais]."—Holotypus, Pohl d.1366 = 1616, K (hb. Benth.)! = NY Neg. 1821; isotypi, +B = F Neg. 1316! F! = F Neg. 54834, K (hb. Hook.)! NY! W!

    M. pogocephala, M. eriocaulis sensu Bentham, 1875: 403.

    M. insidiosa sensu Glaziou, 1906: 178 (15927, P!); non Bentham.

    Erect unarmed, stiffly branched shrubs 8-16 (-20) dm with naked defoliate trunks and leafy homotinous branches 2-4(-5) mm diam., variable in indumentum but the new branchlets silky-villous-tomentose with fine gray or sordid flagelliform setae which lose their sericeous tip when old, the moderately ample subconcolorous, when dry dull brown lfts glabrous except for marginal setae to gray-puberulent beneath or on both faces and sometimes in addition thinly finely setose dorsally, the short-pedunculate, globose or plumply ellipsoid capitula solitary or geminate in the axil of hysteranthous lvs, the young inflorescence pseudoracemose and exserted to ± 1 dm but soon becoming leafy-bracteate, the fruiting capitula lateral and ± immersed in foliage. Stipules firm erect, broadly lanceolate or triangular-acuminate 2.5-7 x 0.8-2 mm, early dry caducous, absent from fruiting specimens. Leaf-stalks including hard pulvinus commonly stout and 2-10 x 1-1.5 mm, at times more slender and elongate to 15 x 0.7 mm, the shallow ventral groove often concealed by vesture; pinnae 1-jug., their rachis to 4.5-8(-9) cm, shorter only in late bracteiform lvs, dorsally rounded and pubescent like stem, carinate ventrally and laterally, shallowly excavate lengthwise between successive pulvinules, the longer interfoliolar segments 2.5-4.5 mm; lfts of longer pinnae (12-)14-20(-23)-jug., abruptly decrescent at base of rachis, more gradually so distally, the small first pair 0.7-1.5 mm distant from lance-subulate paraphyllidia 0.5-1.7 mm, all in outline elliptic-oblong or obliquely ovate from semicordate base, at apex obtuse apiculate or deltately acute, those near mid-rachis (6.5—)7.5—15 x (2.2-)2.5-4.5 mm, 2.4-3.5 times as long as wide, the plane, when dry papery brittle blades 4-5-nerved from pulvinule, the midrib dividing blade ± 1:1.5—2, the one anterior and inner posterior nerves produced well beyond mid-blade, the usually two outer posterior ones shorter, all usually immersed on upper face (exceptionally prominulous), weakly elevated on lower, secondary nervules only rarely perceptible, the discrete marginal setae free at tip for only 0.1-0.5 mm or flagelliform to 1-2.3 mm. Peduncles at anthesis (not well known) less than 1 cm, in fruit 5-22 mm; capitula without filaments 6-8 mm diam., as long or a little longer, prior to anthesis moriform but the obtuse gray-puberulent 4-keeled fl-buds scarcely longer than or ± as long as bracteal cilia; bracts linear-oblanceolate ±2-2.5 mm, setose both dorsally and marginally or simply ciliate, the cilia to 1-1.5 mm; flowers 4-merous 4-androus, some proximal ones staminate and a little shorter; calyx membranous 0.25-0.4 mm, the undulate or subtruncate rim with a few random setulae 0.2-1 mm; corolla narrowly funnelform 2.4-2.9 mm, the cymbiform lobes 0.7-0.9 x 0.6-0.7 mm, densely puberulent externally on either side of glabrous keel; filaments pink, free to base, exserted 5-6 mm. Pods 1-12 per capitulum, sessile, oblong-ellipsoid compressed but turgid 10-16 x 6.5-8.5(-9) mm, 2-4-seeded, the replum 0.7-1.2 mm wide, produced at apex into a conic point 0.5-1.3 mm, the firm valves consisting of livid exocarp ±0.2 mm and crustaceous endocarp ±0.1 mm thick in section, when ripe low-colliculate over each seed, separating in one piece from replum and from each other, the endocarp produced between seeds as a membranous septum 0.3-1 mm wide, the replum and valves alike hispid with crowded erect, basally dilated setae of different calibers, those of replum mostly bulbiform and less than 1 mm, those of valves commonly attenuately flagelliform and attaining 1-2.5 mm, the whole pod resembling a rusty-brown bur.

    In campo rupestre on iron-rich soils, on steep stony hillsides, and in crevices of outcrops, 900-1850 m, locally plentiful about the summits and higher slopes of Sa. do Espinhaço between 19°50' and 21°10'S (Sa. da Piedade and Sa. da Moeda s. to Sa. de Tiradentes) in s.-centr. Minas Gerais, Brazil.-Fl. VI-IX(-I); fr. I-III.

    In 1841, when Bentham described M. pogocephala, M. erinacea and M. eriocaulis, there were only four collections available for comparison, and only one of these showed the fruit. Material accumulated and by 1875 Bentham realized that the first two propositions were based on the flowering and fruiting stages of one species, endemic to central Minas Gerais. No further example of M. eriocaulis had come to hand, and the initial misconception as to its origin in Goiás supported the idea that it was different from the rest, although no better distinguishing characters could be found (Bentham, 1876: 297, in clave) than relatively long peduncles and short floral bracts fully exposing the flower-buds.

    Variation in pubescence of M. pogocephala is related to dispersal but not fully or exactly so. All material seen from Sas. da Moeda, do Curral, do Itabirito and from the immediate environs of Belo Horizonte is characterized by leaflets gray- puberulent on both faces. The type of M. eriocaulis, believed to have been collected on the road between Queluz and Barbacena, has leaflets puberulent beneath only, glabrous above. Both these pubescence-states occur on Sa. da Piedade. Plants from the southernmost known locality on Sa. de Tiradentes also have leaflets glabrous above, and are further peculiar for more explicit venulation and for long-tailed setae. Fruits from this serra are needed to confirm the specific identity. Mimosa pogocephala is apparently replaced on Sa. do Cipó and on Sa. do Caraga by M. bombycina and M. montis-carasae, respectively. The sympatric M. multiplex is readily distinguished by low herbaceous stature and glabrous stems.