Senna subulata

  • Title

    Senna subulata

  • Authors

    Howard S. Irwin, Rupert C. Barneby

  • Scientific Name

    Senna subulata (Griseb.) H.S.Irwin & Barneby

  • Description

    103.  Senna subulata (Grisebach) Irwin & Barneby, comb. nov. Cassia subulata Grisebach, Pl. Lorenz. 82. 1874.—"[Lorentz No.] 250 .. . Catamarca, frequens in collibus pr. Yakutula."—No typus examined, but the pro- tologue definitive. Lorentz 658 from the type-locality, †B, surviving as F Neg. 1751, was perhaps an isotypus.

    Cassia subulata sensu Burkart, 1952, p. 165.

    Slender floriferous bushy shrubs at anthesis 1-3 m with pliantly virgate, often geotropic annotinous branchlets, either glabrous throughout, or the lf-stalks and lower face of lfts minutely strigulose, or the whole plant, including upper face of lfts, villosulous with fine loose wavy hairs up to 0.7-1.2 mm, the foliage bicolored, the thin-textured lfts dull dark green or olivaceous above, pallid beneath, the early racemes axillary to and about as long as ordinary foliage lvs, the lvs at distal nodes abruptly reduced or repressed, the racemes from these axils forming an open, far exserted panicle.

    Stipules early deflexed foliaceous, asymmetrically transversely dilated becoming obliquely reniform but the midrib produced into a subulate point, the lobe further from petiole broader and amplexicaul, the whole blade (point included) 5-12 x 5-33 mm, persistent into or past maturity of the associated lf.

    Lvs 7-19 cm; petiole including firm, laterally dilated pulvinus (2-)2.5-4 cm, at middle (0.5-)0.6-1.1 mm diam, subterete except for narrow ventral sulcus; rachis 3.5-11 cm, its longer interfoliolar segments 1-2.2 cm; gland between proximal (and rarely the second) pair of lfts stipitate, in profile 1.5-3 mm, the lance-ellipsoid or fusiform obtuse or acute head 0.35-0.9 mm diam; pulvinules 1-2.2 mm; lfts (3-)4-6 pairs, accrescent distally, the distal pair narrowly obovate or broadly elliptic-oblanceolate obtuse or subemarginate, minutely mucronulate 2.7-5 x 1-1.9 cm, (2.1-)2.3-3.1 times as long as wide, at base asymmetrically cuneate or on proximal side rounded-subcordate, the membranous translucent margin plane, the midrib immersed above, cariniform beneath, the 7- 10(-11) pairs of slender camptodrome secondary veins often faintly raised on both faces, sometimes immersed but discolored, tertiary venulation imperceptible or erratic, the proximal pairs of lfts proportionately broader and fewer-veined.

    Racemes loosely (7-)15-50-fld, the ascending glabrous or subglabrous obovoid- ellipsoid buds at first racemosely elevated beyond the expanded fls, the axis together with peduncle becoming 5-21 cm; bracts submembranous greenish or livid lance-acuminate 2.5-6 mm, deciduous before full anthesis; pedicels slender, at maturity 10-22 mm; sepals ovate or obovate obtuse submembranous brown- tinged or -speckled, the inner ones broadly hyaline-margined, the set well graduated, the outermost 3-6 mm, the innermost 6.5-11 mm; corolla zygomorphic, the glabrous petals yellow drying stramineous delicately dark-veined, all subsessile, the 3 adaxial broadly obovate or elliptic-obovate, the 2 abaxial narrower and a trifle longer (12-) 13-18 mm, nidulating the long stamens; androecium glabrous, the filaments of 4 median stamens 1.1-2.5 mm, of 3 abaxial ones 4-8.5 mm (that of centric stamen often a little shorter than its neighbors), the 7 fertile anthers thin-walled brownish, those of 4 median stamens almost straight 3.7--4.6 x 0.9-1.1 mm, at apex obliquely truncate 2-porose, those of 3 abaxial stamens lunately lanceolate in profile 4.2-6 x 1.1-1.4 mm, abruptly contracted at apex and 1-po- rose; ovary strigulose or pilosulous; style stoutly linear, gently incurved 2-3.5 x 0.3-0.4 mm, the stigmatic cavity obliquely terminal; ovules 36-60.

    Pod geotropic from pliantly bending central axis, the stipe ±5-6 mm, the cylindric straight or slightly curved body 5.5-6.5 x ±0.5-0.6 cm, abruptly apiculate by persistent style-base, the valves at first smooth lustrous, becoming dull brownish-stramineous papery, indehiscent; seeds stacked in 2 slightly interdigitating files, not seen fully ripe.—Collections: 14.

    Open hillsides and canyon floors near 1200-1700 m in the foothills of the Argentine Andes and detached ranges to the e., from Salta s. through Catamarca, Tucuman and e. La Rioja to the sierras of Cordoba and San Luis, lat. ±25-33°S.

    The foliaceous, obliquely reniform stipules abruptly contracted into an eccentric point (to which the epithet refers) are the obvious hallmark of S. subulata, which otherwise superficially resembles S. pendula sens. lat. except that at full anthesis the upper leaves tend to be reduced or absent and a panicle of flowers is consequently exserted. At close quarters the thin-textured anthers, of which the three abaxial ones are all alike and fertile, recall the androecium of S. (Stipulaceae) organensis and birostris, but the number and orientation of the seeds are typical of ser. Coluteoideae. The species varies greatly in pubescence of the foliage, which may be fully glabrous or villosulous throughout; however we find this variation geographically random and taxonomically insignificant.