Senna velutina

  • Title

    Senna velutina

  • Author(s)

    Howard S. Irwin, Rupert C. Barneby

  • Scientific Name

    Senna velutina (Vogel) H.S.Irwin & Barneby

  • Description

    60.  Senna velutina (Vogel) Irwin & Barneby, comb. nov. Cassia velutina Vogel, Syn. Gen. Cass. 24 & Linnaea 11: 670 (descr. ampliat.). 1837.—"In Brasilia: Manso et Lhotzky leg. in regione Cujaba prov. Matto Grosso [fide Bentham, 1870, p. 118: ‘in saxosis Morro D’Ernesto prope Cuiaba, Silva Manso in Martius herb. Brasil. 220—Holotypus, presumably †B, not seen; neoholotypus, Martius Herb. 220, K! = NY Neg. 1459; isotypus, NY!

    Cassia dysophylla Bentham in Martius, Fl. Bras. 15(2): 117. 1870.—"Habitat in prov. Goyaz, e. gr. . . . prope Salinas: Weddell; . . . prope Conceiçao: Gardner n. 3694; prope Pillar [=Pilar, near Crixas, w.-centr. Goias]: Pohl; ad Rio Paranahyba et Tocantins: Burchell."—Lectoholotypus, Gardner 3694, K (hb. Benth.)! isotypi, †B = F Neg. 1685, BM, K (hb. Hook.)! paratypi, Weddell 2102, K! Pohl 1821, M! Pohl s.n., K! = IPA Neg. 967 = NY Neg. 1458; Burchell 6045, K!

    Cassia velutina + C. dysophylla sensu Bentham, 1871, p. 537.

    Coarsely leafy, erect or diffusely ascending, weakly woody shrubs of rapid growth, at anthesis 1-3 m, densely silky-pilose or -tomentulose throughout, except for sometimes glabrous upper face of lfts, with fine mostly sinuous or entangled, subappressed or partly spreading hairs to 0.5-1.5 mm, the vesture of inflorescence, pods and often of distal (sometimes all) lvs rufous, the foliage bicolored, the lfts above brownish-olivaceous dull or (when glabrous) lustrous, paler beneath, the many-fld racemes of large fls axillary to distal lvs or subpaniculate, not or only shortly exserted from foliage.

    Stipules sometimes persistent, but usually deciduous before the associated lf, (10-) 15-35(-55) mm long, varying from falcately semi-lanceolate-caudate and expanded only at base on exterior side of midrib to broadly semi-cordate-acuminate or caudate with obliquely descending amplexicaul obtuse auricle and a blade expanded on both sides of midrib, the blade at broadest part (2-)3-16(-27) mm wide.

    Lvs (small distal ones disregarded) 11-28 cm; petiole including little differentiated pulvinus (1.2-)1.5-3.2(-4) cm, at middle 1.4-3 mm diam, rounded dorsally, openly shallow-sulcate ventrally; rachis 5-11(-14.5) cm; glands between all pairs of lfts, shortly stipitate or sessile 1.6-3 mm, the stipe when present pilosulous, the body in profile mostly lanceolate acute, sometimes ovate obtuse, 0.4-0.8 mm diam; pulvinules 2.5-4.5(-5) mm; lfts 3-6, in most lvs 3 or 4 pairs, accrescent distally, mostly oblong-, lance- or oblance-elliptic, less often ovate, oblong or obovate, at apex triangular, deltate or obtuse, commonly mucronulate or caudate- acuminulate, the distal pair 4.5-11 x (1.5-)2-4.4(-5) cm, (2-)2.2-3 times as long as wide, at base inequilaterally rounded or subcordate, the margins obscurely revolute, the centric midrib and (9-) 10- 16(- 18) pairs of widely ascending secondary nerves immersed above, prominulous or cordlike beneath, the secondaries mostly more densely rufous-pilosulous than the intervenium, camptodrome only close to margin of blade, the tertiary venulation faint or fully immersed.

    Peduncles stout incurved-ascending 2-8 cm; racemes mostly (6-)10-50-fld, the axis becoming 5-26 cm, the buds elevated above level of at least the earlier fls; bracts deciduous from swelling buds, broadly lance- or ovate-acuminate, acute or caudate (4-)5-11 (- 15) mm; pedicels at and after anthesis 17-37 mm, subtended laterally at base by a hornlike (sometimes deciduous, often eaten) gland 1.5-2.5(-3) mm; buds obliquely obovoid, densely rufous-pilosulous; sepals except for sometimes glabrate submembranous margins firm and pilosulous dorsally, broadly obovate, ovate-elliptic or orbicular, strongly graduated, the smaller outer one 6.5-11.5 mm, the largest inner one 13-18 mm; petals yellow, when dry delicately brown-veined, all pubescent dorsally, the 3 adaxial subsymmetrically ob- ovate-flabellate, the banner often emarginate, these 17-25 mm, the 2 abaxial slightly longer and more oblique, mostly 25-35 mm; filaments pilosulous or puberulent, those of 4 median stamens 1-3 mm, of the central abaxial ones 5-8 mm, of the two latero-abaxial ones dilated (1-1.6 mm wide) 7-12 mm, the anthers glabrous or rarely puberulent in the grooves, those of 4 median ones (in two slightly graduated sets) straight or almost so, (4-)5-8.5 mm, with obliquely divaricate beak 0.4-0.7 mm, that of the centric abaxial stamen slightly incurved 7-10.5 mm, those of 2 latero-abaxial ones lunately incurved 10.5-15.5 mm, the beaks of the 3 abaxial anthers not over 1 mm long, obliquely truncate, those of all anthers 2-porose; style 3.5-5 mm, straight linear, truncate at apex, 0.25-0.4 mm diam; ovules 22-45.

    Pod declined at random angles, often persisting through a full season on annotinous branchlets, the stipe 2-5 mm, the narrowly linear body simply or sigmoidally decurved (10-) 12-22 x 0.3-0.4(-0.45) cm, compressed-quadrangular, carinate by the thick sutures and by a rib running the length of the valves a trifle closer to the dorsal than to the ventral suture, the stiffly papery, densely rusty-pilosulous or -strigulose valves scarcely raised over seeds but marked at the interseminal septa by shallow transverse sulci, these distant 4-7 mm; seeds vertically aligned along pod, in outline oblong or obtusely rhombic (3-)3.3-4.2 x 1.7-2.4 mm, the testa lustrous olivaceous or brown smooth, the oval or elliptic areole 1-1.5 x 0.4-0.8 mm.—Collections: 49.—Fig. 9 (petiolar nectary), 22 (pod).

    Cerrado, usually in red sandy soils, becoming locally abundant in disturbed environments, sometimes forming extensive thickets along roadsides, (200-)400-1050 m, common and widespread over the Brazilian Planalto w. of Rio S. Francisco, from the middle Tocantins valley in Goias w. to the sources of Rio Xingu in Mato Grosso, thence s. through Goias to the upper Paracatu and Pa- ranaiba in w. Minas Gerais, and s.-w. through centr. and s. Mato Grosso just into centr. Paraguay and s.-e. Bolivia; disjunct on Rio Mogi-guaçu in centr. Sao Paulo (mun. Sao Carlos), and remotely so on savannas of upper Mazaruni River in Guyana and along middle Orinoco River in Amazonas, Venezuela.—Fl. (I-)II-VI.

    A handsome but rather coarse senna, which might be considered the prototype of ser. Laxiflorae, notable for the dense, loosely pilose vesture of leaves and flowers, for the characteristic gland at base of each pedicel, and for the narrow compressed pod keeled along each valve by a prominent rib and divided into seed-locules longer than their diameter. It is closely related to the coastal S. australis and to S. cana, vicariant in the drier cerrado and caatinga country to the northeast, which see for differential characterization.

    As implied in the foregoing synonymy, we have drawn the description of S. velutina so as to include Cassia dysophylla Benth. From the first C. dysophylla has been thought to differ only in the narrow deciduous rather than foliaceous and subpersistent stipules, but these, while striking in their extreme expressions, which alone were known to Bentham, are now found to be highly variable. In reality the stipules are never really setaceous from the base, as described for C. dysophylla, but are always a little dilated proximally even though not, at their narrowest, auriculately amplexicaul. From this narrow type of blade we can now trace an uninterrupted series increasing by increment on the side exterior to the petiole, passing through a semicordate into a fully foliaceous type dilated and pinnately veined (like leaflets) on both sides of the midrib. Broad amplexicaul stipules of the velutina type are relatively rare within the whole range of the species as here defined. They have been collected most frequently on the Xingu- Araguaia divide in northeastern Mato Grosso but even here they do not wholly replace the semicordate type, which is associated with precisely the same leaf, flower and pod. Both sorts of stipule were collected at points 20-25 km south of Xavantina (Philcox & Fereira 3838; Hunt & Ramos 5986, both NY), and again far to the east on Sa. Geral northeast of Formosa in Goias (Irwin et al. 15134, 15182, both NY), where narrow stipules appear dominant. Transitions between semicordate and narrowly semi-lanceolate stipules are frequent (cf. Irwin 2530, Mendes Magalhaes 18998, both NY, from between Uberlandia and Monte Alegre in the Minas Triangulo).

    The flowering plants collected by Schomburgk (BM, K) in Guyana seem not to differ in any way from some narrow-stipulate S. velutina from Goias. It is the Cassia arowana Schomb., Reise Guiana, 1206, mentioned by Bentham (1871, p. 582) as a nomen nudum.