Senna angustisiliqua

  • Title

    Senna angustisiliqua

  • Authors

    Howard S. Irwin, Rupert C. Barneby

  • Scientific Name

    Senna angustisiliqua (Lam.) H.S.Irwin & Barneby

  • Description

    168.  Senna angustisiliqua (Lamarck) Irwin & Barneby, comb. nov. Cassia angustisiliqua Lamarck, Encycl. Meth. 1: 649. 1785.—Typus infra sub var. angustisiliqua indicatur.

    Shrubs and treelets at anthesis 1-4.5 m, with twiggy, often tortuous branches and densely leafy, virgately erect, ascending-incurved or plagiotropic hornotinous branchlets, varying from quite glabrous below the ovary to variably pilosulous with fine spreading-incurved, gray or yellowish hairs up to 0.2-0.65 mm commonly mixed with short clavate-glanduliform ones, the foliage bicolored, the lfts dark dull green and glabrous above, paler but either glabrous or pubescent beneath, ciliolate or not, the subumbellately (l-)2-4-fld racemes mostly axillary to coeval lvs and shorter than them, sometimes crowded together on short leafy axillary sideshoots.

    Stipules erect, narrowly linear-attenuate or setiform (1.5-)2.5-7(-10) x 0.15-0.5 mm, early deciduous.

    Major lvs (deciduous, sometimes lacking from specimens in late fl or from arid sites) 5-12(-13) cm; petiole including discolored pulvinus 6-28 mm, 1-3 times as long as first segment of rachis, rounded dorsally, narrowly grooved ventrally; rachis 2-9.5 cm; petiolar glands between the proximal or 3 proximal pairs of lfts, erect, stipitate or subsessile, including stipe 1.3-3.5 mm tall, the orange or yellowish body compressed or (when narrow) subterete, acute 0.4-0.8(-l) mm diam; pulvinules 0.5-1 mm; lfts 4-14 pairs, scarcely or markedly accrescent upward, in outline oblong-elliptic to -obovate, abruptly acute, obtuse mucronulate or rarely emarginate, the distal pair (10-) 11-33 mm (further described under vars.), at base asymmetrically cuneate or rounded, the margins revolute, the straight centric midrib immersed above, cariniform beneath, giving rise to (4-)5-8(-9) pairs of fine camptodrome (and often a few intercalary) secondary veins prominulous beneath, not or scarcely so above, the tertiary venulation immersed or faintly visible beneath only.

    Peduncles (0.7-)1-3 cm; racemes subumbellately (l-)2-4, many exactly 2-fld, the axis 0-4.5 mm; pedicels at anthesis subfiliform, in fruit little thickened (8-) 10-28 mm, subtended on one side by a sessile or short-stipitate subuliform-ellipsoid gland; bracts oblanceolate cucullate 1.3-3.5 mm, shielding the very young bud but deciduous with first elongation of pedicel; buds subglobose, glabrous or thinly pilosulous; sepals green or yellowish with pallid membranous margins, obovate-orbicular, strongly graduated, the large inner ones 5-8 mm; petals yellow, dorsally pilosulous or at least near claw puberulent, erratically heteromorphic, 3 adaxial smaller, symmetrically or asymmetrically oblanceolate or obovate, among themselves either similar or dissimilar in size and shape, the 2 abaxial larger, 16-28 mm, one obliquely obovate, opposed to the divergent pistil, one (often largest of all) obliquely reniform, loosely nidulating the long stamens; androecium glabrous except for sometimes puberulent filaments; filaments of 4 median stamens ± dilated 1.1-1.8 mm, of 3 abaxial ones filiform (l-)2.2-4.7 mm, all free to base; anthers of 4 median stamens little incurved 2.5-5 mm, the depressed beak 0.2-0.5 mm dehiscent by one U-shaped pore, of 3 abaxial ones lunately incurved, the body 4-5.5 mm, the tubular beak erect 1-1.8 mm, slightly dilated at 1-pored apex; ovules 16-26.

    Pod pendulous or obliquely spreading, the stipe 3-5.5 mm, the linear body straight or slightly decurved (3-)4.5-8 x 0.5-9.5 cm, the chartaceous or casta- neous, finally nigrescent, thinly pilosulous or glabrate valves slightly depressed between each seed and simply mounded over them; seeds (of var. angustisiliqua and inaguensis, those of var. fulgens not seen) compressed-obovoid or subquad- rately ovoid 3-4.6 x 1.8-3.6 mm, the testa brown, dull or sublustrous, the ovate- elliptic areole 1-1.4 x 0.4-0.7 mm.

    As mentioned in our discussion of S. pallida sens, lat., Cassia angustisiliqua with C. crista and C. fulgens, all of which were reduced by Bentham to C. biflora, are more closely related to S. viciifolia and S. robiniifolia, forming with them and Central American S. tonduzii a vicariant series collectively characterized by the U-shaped dehiscence of the four median anthers. As here defined so as to accommodate the plants of Hispaniola and Jamaica that have passed latterly as C. biflora, to which we here add the local south Bahaman Peiranisia inaguensis, S. angustisiliqua differs from S. robiniifolia of eastern Cuba and Caribbean South America in the smaller leaves usually more shortly petioled and lacking glands beyond the second or third pair of leaflets, in the shorter, commonly obtuse leaflets, in the free median and adaxial filaments, and in the shorter pod of which the ripe valves remain continuous until after dehiscence, not fragile along the lines of the interseminal septa. The Jamaican S. angustisiliqua var. fulgens, with more than one petiolar gland and leaflets rather larger than those of genuine var. angustisiliqua of Hispaniola, is to that extent intermediate to Cuban S. robiniifolia, expressing a relationship that might be anticipated by study of the dispersal of these probably recently divergent forms.

    Key to the Varieties of S. angustisiliqua

    1. Beak of 4 median anthers lateral, divergent from the theca at ±90°; petioles 6-15(-18) mm, mostly 1-2 times as long as the first interfoliolar segment of rachis; Hispaniola, Jamaica.

    2. Petiolar gland between proximal pair of lfts only; pod (3-)4.5-7.5(-8) x 0.5-0.7(-0.8) cm; Hispaniola.

    168a. var. angustisiliqua (p. 515).

    2. Petiolar glands between 2-3 lowest pairs of lfts; pod 10-12 x 0.8-0.95 cm; Jamaica.

    168b. var. fulgens (p. 516).

    1. Beak of 4 median anthers terminal suberect, projecting beyond the theca; petioles 13-28 mm, mostly 2-3 times all long as the first interfoliolar segment of rachis; s.-e. Bahamas (Inagua, Caicos). Glands between 1, 2 or 3 pairs; pod 6-9 x 0.7-1.1 cm.

    168c. var. inaguensis (p. 516).