Senna cornigera H.S.Irwin & Barneby
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Authors
Howard S. Irwin, Rupert C. Barneby
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Authority
Irwin, Howard S. & Barneby, Rupert C. 1982. The American Cassiinae. A synoptical revision of Leguminosae tribe Cassieae subtrib Cassiinae in the New World. Mem. New York Bot. Gard. 35, part 1: 1-454.
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Family
Caesalpiniaceae
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Scientific Name
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Type
Holotypus, R; isotypi, K, NY, US.
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Description
Species Description - High-climbing vine flowering in forest-canopy, the rope unknown, the hornotinous branchlets terete striate, appearing glabrous throughout but the lower face of lfts and axes of inflorescence minutely strigulose with appressed hairs to 0.15 mm, the foliage bicolored, gray-olivaceous sublustrous above, brownish dull beneath, the inflorescence of simple racemes or of short leafless few-branched panicles arising from axils of living lvs, shortly or not exserted. Stipules caducous, not present on material seen. Lvs 16-20 cm; petiole including wrinkled discolored pulvinus 6-16 mm, at middle 1.7-2.5 mm diam, openly shallowly sulcate, much shorter than rachis; rachis 4-5.5 cm, produced beyond distal pair of lfts into a rigidly vulnerant, abruptly divaricate, distally slightly incurved, horn-shaped appendage (seta) 7-10 mm; gland 1 sessile between proximal pair, plumply deltate-linguiform obtuse ±3-4 mm, glabrous; pulvinules strongly wrinkled 3-5 mm; distal pair of lfts sub- symmetrically broadly ovate, very shortly deltate-acuminate, 10-14 x 7-8.5 cm, at base rounded-subcordate on proximal and broadly cuneate-rounded on distal side, the margin re volute, the slender straight centric, ventrally immersed midrib with ±8-10 pairs of major camptodrome, ventrally prominulous secondary veins all sharply cariniform beneath; the tertiary and reticular venulation more evident above than beneath; proximal pair of lfts similar, ±2/3 as long. Peduncles 2.5-8.5 cm; racemes loosely openly 12-25-fld or some subterminal to the panicle only 2-5-fld, the axis (1-)3-11 cm; bracts ovate obtuse 2-3 mm, persistent into anthesis; pedicels at full and late anthesis 4-5.5 cm; buds globose glabrous; sepals submembranous yellowish, all broadly ovate-orbicular obtuse, strongly graduated, the 2 large innermost 11-15 mm, the small outermost scarcely half as long; petals yellow, puberulent dorsally along major veins, somewhat heteromorphic, the adaxial one broadest ±25 x 22 mm, beyond the short claw suborbicular-emarginate, the two lateral similar except a trifle shorter and obtuse- truncate, the two abaxial slightly longer and proportionately narrower, broadly oblance-obovate up to 26-30 x 16 mm, one of them cupping the two longest stamens; androecium functionally 7-merous, the filaments remotely minutely puberulent, of 4 median stamens 2.5-3 mm, of 1 abaxial stamen 3-4 mm, of 2 abaxial ones 6.5-8 mm, the anthers glabrous, of 4 median stamens nearly straight 5-7 mm, contracted into a very short obtuse 1-porose beak ±0.5 mm, of 3 abaxial ones strongly incurved and 12-15 mm, contracted into a porrect beak ±1.5 mm; ovary densely strigulose, the short style very slightly dilated, ±0.5 mm diam at the bend below the stigma, the orifice 0.3 mm diam; ovules (1 count) 154. Pod not seen fully formed, when young narrowly ribbonlike up to 2 dm.— Collection: 1 (typus).—Fig. 18.
Distribution and Ecology - Forest, on terra firme, probably below 250 m, known only from the type-locality on Rio Jari in n.-e. Brazil.—Fl. X-XI.
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Discussion
A notably distinct species, characterized by the syndrome of short-petiolate leaves, subsymmetrically ovate leaflets, large flowers with highly differentiated stamens, and especially by the seta terminating the leaf-stalk, here modified into a stout, divaricate, prickle-like horn. The flower and leaflet-shape suggest S. georgica, which differs in its much longer petioles (2-6, not 0.6-1.6 cm), and in the filiform, early dry and deciduous seta. The very young pod of S. cornigera resembles that of S. georgica at the same stage of growth, and it is possible that the seeds of S. cornigera will also be found to be uniseriate. The remarkable hornlike seta must be related to the liane habit of S. cornigera, found by the collector climbing a tree 35 m tall; it could well function as a grappling hook like the similar but backwardly hooked seta of remotely allopatric Peruvian S. uncata which combines with almost the same flower a reportedly arborescent growth- habit, substantially smaller leaves subtending the racemes and plane-margined leaflets.
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Distribution
Brazil South America|