Senna reniformis

  • Title

    Senna reniformis

  • Author(s)

    Howard S. Irwin, Rupert C. Barneby

  • Scientific Name

    Senna reniformis (G.Don) H.S.Irwin & Barneby

  • Description

    57.  Senna reniformis (G. Don) Irwin & Barneby, comb. nov. Cassia reniformis G. Don, Gen. Hist. Diehl. Pl. 2: 440. 1832.—"Native of Brazil, Sello."—Holotypus, presumably once in herb. Lambert., not found; neo- holotypus, Sellow s.n., K! = IPA Neg. 991 = NY Neg. 10480.

    Cassia reniformis sensu Vogel, 1837, p. 25-26, cum var. ß; Bentham, 1870, p. 124; 1871, p. 547.

    Amply leafy, weakly arborescent shrubs at anthesis (1-)2-6 m, highly variable in pubescence, the smooth or bluntly ribbed annotinous branchlets, lf-stalks and one or both faces with margins of lfts minutely puberulent, or both pilosulous and puberulent, or simply pilosulous, with spreading-ascending or subappressed, pallid or lutescent hairs to 0.1-0.6 mm, or sometimes subglabrous throughout, the lft-blades always sprinkled with minute orange or livid thickened trichomes, the foliage moderately 2-colored, the chartaceous brownish-olivaceous blades dull or sublustrous, a little paler beneath, the inflorescence an exserted subcorymbose panicle of racemes.

    Stipules foliaceous persistent amplexicaul, in outline semi-ovate-auriculate 11-33 x 6-18 mm, the descending auricle broadly rounded, the erect or incurved tip deltately acute, triangular or subulate-caudate, the whole blade flabellately several-nerved on broad side of midrib, this sometimes exactly marginal, always very strongly displaced.

    Lvs 18-28 cm; petiole including little-swollen discolored pulvinus 1.2-4(-5) cm, at middle 1-3.3 mm diam terete or bluntly carinate dorsally, shallowly open- sulcate ventrally; rachis (3-)4-9.5(-12.5) cm; glands between all pairs of lfts sessile or stoutly short-stipitate 1-2.4 mm tall, the squatly ovoid to slenderly lance- ellipsoid, usually acute head 0.4-1.5 mm diam; pulvinules stout wrinkled 2-5 mm; lfts (2-)3-5, commonly 3 or 4 pairs, little or conspicuously accrescent upward along rachis, in outline ovate- or obovate-acuminate to ovate- or lance-elliptic, rarely ovate obtuse, the distal pair 4.5-12 x 1.7-4.5(-5) cm, 2-3(-3.2) times as long as wide, at symmetrical base varying from broadly cuneate to rounded or (when broad) subcordate, the margins revolute, the centric straight midrib impressed above, cariniform beneath, the 6-13 pairs of major camptodrome and irregular intercalary secondary veins with subsequent reticulate venulation prominulous on both faces, sometimes only faintly or bluntly so above, sharply so beneath.

    Peduncles stout incurved-ascending (1-)3-12 cm; racemes (5-)10-35-fld, the axis becoming (1-)2-20 cm; bracts (caducous, little known) narrowly lanceolate or lance-caudate 3-6 mm; pedicels at and after anthesis ±2-4 cm, charged laterally near or well above middle with a substipitate ellipsoid or conic acute gland 1.3-2.5 mm; fl-buds obliquely obovoid-ellipsoid obtuse, externally puberulent at base, the inner sepals glabrous dorsally, minutely ciliolate; sepals subpetaloid yellowish but toward middle greenish or red-tinged, all elliptic-obovate to suborbicular, strongly graduated, the small outer ones (4.5-)5-9 mm, the innermost 12-16 mm; petals yellow, when dry finely brown-veined, glabrous or dorsally puberulent along and near the claw, in outline like those of C. corifolia, the long abaxial ones up to 21-32 mm; androecium glabrous, the filaments of 4 stamens 2-3.5 mm, of 2 latero-abaxial ones dilated (0.8-1.5 mm wide) 7-10 mm, of the central abaxial one 5-7 mm, the anthers of 4 medium stamens 4-8 mm, obliquely truncate and little curved, of the central adaxial stamen similar but 7-9 mm, of 2 latero-abaxial ones (6-)9.5-13 mm lunately incurved, the beaks of all 0.5-1 mm, biporose, those of the 4 medium divaricate, those of the rest obliquely erect; ovary pilosulous, puberulent, or both; style linear straight 4.5-8 mm, subsym- metrically truncate at apex and there 0.25-0.4 mm diam; ovules (30-)32-46.

    Pod erratically declined or pendulous, the stipe 2-5 mm, the linear piano-compressed, usually decurved body (7-) 10-19 x 0.9-1.2 cm, carinate by the cordlike straight or undulately constricted sutures, the livid-castaneous, finely transverse- venulose, finally stiffly chartaceous and nigrescent valves scarcely elevated over seeds, the interseminal septa thick but narrow, 3.5-5 mm apart; seeds (few seen) narrowly oblong in outline ±6x2 mm, bluntly compressed-quadrangular, the testa smooth lustrous castaneous, the linear-elliptic areole ±4 x 1 mm.—Collections: 56.

    Cerrado, margin of gallery forest, thickets in brejo, and about rock outcrops, commonly on quartzitic and ‘canga’ soils, (800-)950-1800 m, scattered along the crest and both slopes of Sa. do Espinhaço, between 16°30' and 20°30'S, in centr. Minas Gerais; apparently disjunct on the Pardo-Contas divide near 14°50'S in s.-e. Bahia.—Fl. (XII-)II-VIII, the pods long persistent.

    A handsome floriferous senna, readily recognized by the syndrome of reflexed foliaceous stipules, broad leaflets symmetrical at base, pedicels charged above middle with a stalked gland, and broad piano-compressed pod. The partly sympatric S. cana is similar in the stipules, but has basally oblique leaflets, the gland at base of the pedicels, and a much narrower tetragonal pod.

    Specimens labelled "Riedel 526. In ripa rivi Guapore, apr. 1828" (LE) are probably associated with the wrong ticket. It seems unlikely that S. reniformis, otherwise endemic to Sa. do Espinhaço, should occur on the Brazil-Bolivia border in northeast Mato Grosso or Rondonia where Riedel found himself in April of 1828. Interestingly enough Bentham, who saw and correctly identified these specimens, cited in Flora Braziliensis only Riedel’s collection from Minas Gerais.