Senna urmenetae

  • Title

    Senna urmenetae

  • Authors

    Howard S. Irwin, Rupert C. Barneby

  • Scientific Name

    Senna urmenetae (Phil.) H.S.Irwin & Barneby

  • Description

    100.  Senna urmenetae (Philippi) Irwin & Barneby, comb. nov. Cassia urmenetae Philippi, Anal. Univ. Chile 41: 708. 1872.—"De la alta cordillera de la provincia de Santiago."—Holotypus (SGO 50702, fide Munoz Pizarro, 1960, p. 73), not seen; isotypi, †B = F Neg. 1762, NY, W!—Philippi s.n., G, though dated 1876, may be isotypic also.

    Cassia glaucescens Bentham, Trans. Linn. Soc. London 27: 539. 1871.—. . Chile, near Co- piapo, Pearce."—Holotypus, collected at 8000 ft in Cordillera de Copiapo, XI. 1863, K! = NY Neg. 1569.—The associated pods, accepted as pertinent by Bentham, represent S. ay mar a Irwin & Barneby collected by Pearce near La Paz in 1865, probably misplaced in mounting.—Non C. glaucescens Hoffmannsegg, 1824.

    Cassia oreades Philippi, Anal. Univ. Chile 84: 443. 1893.—"In Andibus provinciae Santiago januario 1878 lecta fuit."—Holotypus, SGO 39978 or 50704 (fide Munoz Pizarro, 1960, p. 73), not seen; presumed isotypi †B = F Neg. 17201 distributed by F. Philippi as "Cassia cumingii" without further data, BM!—Equated by Reiche, 1897, p. 38 with C. urmenetae.

    Cassia urmenetae sensu Reiche, 1897, l.c.

    Bushy shrub 3-10 dm, the leafless old trunks clad in smooth brown, ultimately fissured bark, the densely leafy hornotinous branchlets and foliage pallid olivaceous and pilosulous throughout or almost so with fine, vertically erect pallid hairs 0.1-0.3 mm, the concolorous, dull or scarcely lustrous, usually thick-textured lfts sometimes glabrescent above in age, the few-fld leafy-bracteate racemes arising from distal axis to form a small, scarcely exserted corymbose panicle.

    Stipules erect, subulate or setiform 0.5-2 mm, early dry caducous.

    Lvs (2-)2.5-6 cm; petiole including moderately dilated, scarcely wrinkled pulvinus (3-)4-13(-15) mm, at middle 0.6-1 mm diam, rounded dorsally, deeply narrowly grooved ventrally; rachis (0-)4-22 mm; pulvinules 0.4-1 mm; gland between proximal (or only) pair stipitate, in profile 0.7-1.6 mm tall, the slenderly subuliform acute body 0.15-1.3 mm diam; lfts (1-)2-4 pairs a little accrescent distally, in outline most often lanceolate or lance-elliptic, rarely broader and ovate, in either case deltately acute mucronulate, the distal pair 16-28 x 3.5-9(-12) mm, (1.7-)2-5 times as long as wide, at base asymmetrically rounded or broadly cuneate, the margin plane, the centric midrib alone prominulous on dorsal face, the blades otherwise veinless superficially or with 4-6 pairs of either simple or weakly camptodrome secondary venules weakly bluntly prominulous beneath.

    Racemes loosely 3-6-fld, the axis together with peduncle becoming 2.5-7 cm; bracts (caducous, little known) subulate ±1-2.5 mm, exceptionally modified into depauperate lvs; pedicels in fruit 12-17 mm; fl-buds obovoid glabrous; expanded fls not seen; ovary pilosulous; style ±1-1.5 mm; ovules 8-12.

    Pod obliquely declined from ascending pedicel, the densely minutely pilosulous stipe 2.5-4 mm, the linear but nearly always undulately constricted, straight or gently declined body 5-7 x 0.7-0.9 cm, cuneate at both ends, bicarinate by the cordlike sutures, laterally compressed but turgidly expanded over developed seeds, the valves becoming papery stramineous or brownish, prominently venulose, sparsely minutely puberulent at maturity, the membranous interseminal septa complete, the locules ±7-9 mm long; seeds obovoid or obtusely rhombic-obovoid 6.5-7 x 4.5-5.2 mm, a little compressed parallel to the valves, the smooth testa olive-drab or brownish-olivaceous, not or scarcely lustrous, the cordate or ovate areole 2.4-3 x 1.4-2 mm, commonly emarginate proximally.— Collections: 5.

    Dry rocky slopes and talus, 1550-2500 m, along the Chilean slope of the Andes in lat. 27°-33°S, from centr. Atacama s. to Santiago—Fl. X-I.

    This still imperfectly known montane xeromorphic senna is apparently related to S. arnottiana, which resembles it in habit but differs in the broadly obovate or elliptic-oblong, not lanceolate (rarely ovate) leaflets, the broader pod, and the seeds turned edgewise to the valves and facing the septa, not oriented in the ordinary way with the broad faces opposed to the valves. The scanty material of S. urmenetae falls into two groups: three collections from departments Copiapo and Vallenar in central and southern Atacama, characterized by two to three pairs of thick-textured leaflets essentially veinless externally ; and two from Cordillera de Santiago in which the three to four pairs of slightly thinner-textured leaflets are faintly penniveined dorsally. Although we have not seen fully expanded flowers, which could, of course, furnish surprising differential characters, we judge these to be in a broad sense conspecific, for they involve no greater phenetic diversity than is well documented in S. arnottiana. Exploration of montane Coquimbo, from which we have as yet no record for S. urmenetae, must be expected to disclose geographically intermediate populations which will obviously be crucial in final evaluation of the species.

    Bentham singled out his Cassia glaucescens as a connecting link between his Chamaesennae Pachycarpae and his Chamaefistulae Brachycarpae, but he had at the time no means of guessing that the material at his disposal consisted of a mixture of flowering S. urmenetae and misplaced fruits of S. aymara.