Senna cernua

  • Title

    Senna cernua

  • Author(s)

    Howard S. Irwin, Rupert C. Barneby

  • Scientific Name

    Senna cernua (Balb.) H.S.Irwin & Barneby

  • Description

    136.  Senna cernua (Balbis) Irwin & Barneby, comb. nov. Cassia cernua Balbis, Cat. Stirp. Hort. Bot. Taur. ad annum mdcccxiii 22. 1813 (jan).— "Colitur in olla . . . Semina hujusce plantae accepi a D. Armano sub nomine Cassiae ex America meridionali."—No holotypus seen, but authentic vouchers survive: misit Balbis, BM (hb. Shuttle worth, ex hb. Roemer.); sent to Schreber from Torino by Balbis, and to Fischer from Montpelier by Delile, both LE (NY Negs. 10497, 10498; in hb. Desfont., FI (hb. Webb.)!—Improperly reduced by Colladon, 1816 and by DeCandolle, 1825, 11. cc. infra, with the slightly posterior C. sulcata.

    Cassia sulcata DeCandolle, Cat. pi. hort. Monspel. 90. 1813 (feb-mar).—"Ab hortis Italicis recepi sed patriam ignoro."—Holotypus, "ex hort. meo, 5.XIII. 1812," G-DC! presumed isotypus, acquired by Fischer from Delile, LE! subsequently cult, at Montpellier, IX. 1822, MPU!

    Cassia macrocarpa Micheli, Mem. Soc. Phys. Geneve 28(7): 43, pl. 16. 1883.—"[Paraguay]: Caaguazu in campis, Mart., [Balansa] n. 1404."—Holotypus, collected 7.III. 1876 (fl, fr jun), G! isotypus, P!

    Cassia sulcata sensu Colladon, 1816, p. 110, t. 6; DeCandolle, 1825, p. 498; Bentham, 1870, p. 112; 1871, p. 531; Glaziou, 1905, p. 160.

    Cassia leptocarpa sensu Chodat & Hassler, 1904, p. 692, quoad no. 7050; non Bentham.

    Cassia sophera sensu Glaziou, 1905, p. 160, quoad no. suum 13748; non Linnaeus.

    Coarse, amply leafy, softly woody subshrubs 0.8-1.6 m, with sulcate, obtusely angulate, distally flexuous annotinous stems, except for always glabrous upper face of lfts strigulose-pilosulous throughout with appressed straight or subappressed incurved or wavy hairs up to 0.25-0.6 mm, the ill-scented foliage strongly bicolored, yellowish-green above, pallid or bluish-green (and when young often subsericeous) beneath, the short racemes either all axillary to and much surpassed by fully developed lvs or some distal ones forming a narrow thyrsiform panicle.

    Stipules erect, thinly herbaceous, brown or reddish-tinged, lanceolate or lance-acuminate 3-7 x 0.4-1.2 mm, very early dry caducous, absent from many flowering and most fruiting spms.

    Major lvs (below and sometimes through part or most of inflorescence) 15-29 cm; petiole including ± wrinkled and discolored pulvinus (2.5-)3.5-9 cm, at middle (0.8-) 1-2.4 mm diam, rounded dorsally, thick-margined and openly shallowly sulcate ventrally; gland contiguous to pulvinus, sessile or almost so, globose or plumply ovoid obtuse or inversely pyriform 1-2.5 x 0.9-2.2 mm, either a little longer or a little shorter than its diam, exceptionally a second gland between proximal pair of lfts; rachis (6.5-)8-17 cm; lfts (5-)6-8(-9) pairs, moderately or markedly accrescent upward but the distal pair sometimes a little shorter than the penultimate, the longest pair oblong- to obovate-elliptic or broadly oblanceolate obtuse, deltately subacute or rarely acuminulate, often mucronulate, (2.8-)3.3-6(-7) x (1.1-)1.3-2.6 cm, 2.1-3.2 times as long as wide, the translucent orange margin plane except at inequilaterally cuneate or rounded base where incipiently revolute, the straight centric midrib immersed above, cariniform beneath, the 8-12 pairs of slender camptodrome (and random intercalary) secondary veins finely prominulous above, more sharply so beneath, the tertiary venulation fully immersed or faint and irregular.

    Peduncles 8-26(-30) mm; racemes (3-)5-12(-17), exceptionally -25)-fld, the axis together with peduncle becoming (1-) 1.5-5(-7) cm; bracts ovate or lanceolate 2-4.5 x 0.8-1.5 mm, early dry castaneous, caducous from first elongation of pedicel; mature pedicels 15-25 mm; fl-buds nodding obovoid or subglobose, strig- ulose-pilosulous or sometimes glabrescent distally; sepals obovate obtuse, the firm outer ones commonly brownish-tinged 5-7.5(-8) mm, the inner subpetaloid glabrescent, palmately veined from base, the longest 7.5-11 mm; petals withering in afternoon of first day, glabrous, rich yellow drying ochroleucous or whitish brown-veined, the vexillar one flabellate-obcordate, the 2 lateral obovate obtuse, the 2 abaxial ones narrowly obovate or oblanceolate, the longest petal 14.5-20 mm; androecium glabrous, functionally 7-merous, the spatulate-obcordate staminodes 1.7-2.4 mm wide, the filaments of 4 median stamens 1.4-2.1 mm, of 2 latero-abaxial ones dilated 7-9.5 mm, of the centric abaxial one 2.5-4 mm, the 4 median anthers including their short, obliquely dilated beak 4.6-6.2 mm, the sterile abaxial one 3.5-5.5 x 0.8-1.4 mm, the 2 large brown abaxial ones 5.6-7.7 x 2-2.6 mm measured from sagittate base to strangulated base of beak, the beak itself 1.3-1.7 mm, the thickened linguiform pollen-cup prolonged 0.8-1.1 mm beyond the opposed umbos; ovary densely strigulose-pilosulous, commonly canescent; style grooved ventrally 2.5-3.6 mm, abruptly incurved and thickened distally, there 0.6-0.8 mm diam, the introrse stigmatic cavity barbellate; ovules (60-)76-94.

    Pod ascending or erect, straight or curved outward (and sometimes sigmoidally twisted), narrowly linear 19-28 x 0.3-0.45 cm, in compression and texture of valves exactly like that of S. hirsuta var. hirta, the seminal locules 2.2-4 mm long, thus either longer or shorter than wide; seeds oriented and compressed so as to fit their locule, either plumply ovoid compressed parallel to valves or drumshaped compressed parallel to septa, their wider faces 2.5-3.1 x 2-2.6 mm, the testa as in S. hirsuta, the areole elliptic 1.3-1.5 x 0.7-1 mm.—Collections: 54.

    Campo and cerrado, but now commonly seen only in disturbed brush-woodland, along roads, in pastures (where shunned by cattle), and in ruderal or waste places, mostly 300-800 m but in Sa. do Espinhaço ascending to 1500 (on Sa. da Piedade to 1800) m, locally abundant in scattered colonies around the s.-e. margins of the Brazilian Planalto from centr. Minas Gerais (Sa. do Cabral and Diamantina) to interior montane Rio de Janeiro (Petropolis), e. Sao Paulo and n.-e. Parana; collected in early times, but not recently, in s. Goias near 16°S (Jaragua; Luziania); apparently native but disjunct in s.-e. Paraguay (Rio Apa; Valenzuela; Caaguazu), to be sought in s.-w. Mato Grosso.—Fl. (X-)XI-IV.

    Senna cernua is readily distinguished from allied Basiglandulosae by the long-petioled leaves and relatively numerous (about 6-8) pairs of oblong- or obovate- elliptic leaflets, these combined with the extremely long and narrow pod of S. hirsuta var. hirta. A rather coarse, ill-scented plant, weedy in nature, it flourishes in cultivation with the minimum of attention, becoming an attractive object when in advanced anthesis, as the leaves then become abruptly reduced in size and the racemes are gathered into erect, exserted thyrses.

    Since the days of DeCandolle and Colladon this species has been known consistently as Cassia sulcata, but the eclipsed epithet cernua must be restored under the present Code. It seems virtually certain, although not specifically stated, that DeCandolle received the seeds of his C. sulcata from the Turin botanic garden, where Balbis was growing the same thing as C. cernua. We surmise that the stock grown in Italian gardens, and thence disseminated to Montpelier and Schonbrunn, may have been raised from seed brought from Brazil by Raddi.