Senna organensis (Harms) 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
Typus infra sub var. organensi indicatur.
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Synonyms
Cassia organensis Harms ex Glaz.
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Description
Species Description - Shrubs of rounded outline, some arborescent in age, at anthesis 0.7-3 m, with brown or pallid subterete, sometimes striped or lenticellate branchlets naked after first season but densely leafy distally, these and lf-stalks thinly subappressed- pilosulous or more densely hirsutulous with pallid or lutescent hairs up to ±0.2-0.55 mm, the foliage bicolored, the lfts either dull or lustrous olivaceous above, paler and sometimes glaucescent beneath, ciliolate or not but facially glabrous except for a tuft of hairs sometimes present in proximal angle of midrib beneath, the racemes all axillary to distal lvs, the subcorymbose fls immersed in foliage or shortly exserted. Stipules subfoliaceous erect, straight or incipiently falcate, in outline oblanceolate attenuate downward and sometimes acuminate distally, (5-)6-15 x 0.7-6(-7) mm, tardily deciduous. Lvs (4-)5-11.5 cm; petiole including dilated pulvinus 0.6-3.5 cm, rounded dorsally, narrowly sulcate ventrally; rachis (1.2-)2-6 cm; pulvinules 1-2.2 mm; glands between proximal or between all pairs of lfts, shortly stipitate, in profile 0.8-2 mm, the obovoid or ellipsoid obtuse or acute body 0.3-0.8 mm diam; lfts 3-8 pairs, accrescent upward, in outline broadly obovate, oblong-obovate, -oblanceolate or broadly oblong-elliptic, obtuse or emarginate, the distal pair (13-) 18-44(-45) x (7-)9-22 mm, 1.8-2.5 times as long as wide, at base broadly cuneate to rounded or cordate on proximal side, narrower on distal one, the straight centric midrib with 5-8 pairs of camptodrome secondary veins either prominulous or immersed, the tertiary venulation sometimes prominulous and reticulate on one or both faces. Peduncles 2.5-5.5 cm; racemes at first densely (5-)10-35-fld, the axis becoming (0.6-) 1-4.5(-6) cm, the expanded fls raised ± to level of unopened buds; bracts resembling stipules in shape and texture (3-)4-8 x (0.8-) 1-2.2 mm, persistent into full anthesis; pedicels 12-28 mm; fl-buds globose, the sepals glabrous except for sometimes minutely ciliolate margins; sepals except for pallid membranous margins firm brownish or red-speckled, little graduated, all broadly obovate-suborbicular, the inner ones ±4.5-6.5 mm; petals glabrous yellow, when dry paler and arborescently brown-veined, subhomomorphic except the banner slightly longer or wider (or both) and the abaxial pair a trifle more oblique, all obovate- cuneate or -flabellate obtuse or emarginate, the longest 7-12 mm; androecium glabrous, the filaments of 4 median stamens ±2-2.5 mm, of 3 abaxial ones 2-5.5 mm, the anthers (when dry dark brown) of 4 median stamens oblong almost straight 2-4.5 mm, of 3 (or 2) abaxial ones gently incurved 3.2-6.5(-7) mm, all abruptly contracted and truncate at apex, shortly bluntly sagittate at base; ovary glabrous or strigulose, the style 1-2 mm, not dilated and only 0.2-0.3 mm diam immediately beneath stigma; ovules (6-)8-14. Pod (of vars. organensis and extratropica, otherwise unknown) spreading at random angles or declined, the stipe 1.5-4 mm, the oblong almost straight piano- compressed body (3-)3.5-6.5 x 1.1-1.5(-1.7) cm, prominently margined by sutures, the purplish-brown, finally papery valves scarcely raised over seeds, the intraseminal septa very narrow, 4-5 mm apart; seeds oblong-obovate compressed 6-7.5 x 4-4.5 mm, the testa atrocastaneous lustrous, a large shadowy spot but not truly differentiated areole on either face.
Variety Key - Key to the Varieties of S. organensis 1. Filaments of 3 abaxial stamens 2-3 mm and their anthers ±3-4 mm long; range of the species. 2. Lfts 4-8 pairs; gland between proximal and some distal pairs of lfts; venulation of upper face of lfts immersed or very faintly raised; ovary strigulose; Rio de Janeiro and adjacent Minas Gerais-Espirito Santo. 104a. var. organensis (p. 328). 2. Lfts 3-5 pairs; gland between proximal pair only; venulation of both faces prominulous, at least in mature blades; ovary glabrous; e. Parana. 104c. var. extratropica (p. 328). 1. Filaments of 2 or 3 abaxial stamens 4.5-5.5 mm, their anthers 5-7 mm long; local on Sas. da Mantiqueira and dos Orgaos in Rio de Janeiro. 3. All 3 abaxial stamens elongate and subisomorphic, fertile; gland between proximal pair of lfts only or between proximal and 1-2 penultimate pairs; lfts relatively thin-textured, the distal pair oblanceolate ±10-13 mm wide; Sa. da Mantiqueira, especially on Mt. Itatiaia. 104b. var. heterandra (p. 328). 3. Two antepetalous abaxial stamens elongate and fertile, the centric one between them much smaller and sterile; glands between all but distal pair of lfts; lfts notably coriaceous, the blade of the distal pair oblong-obovate 13-22 mm wide; Sa. dos Orgaos. 104d. var. friburgensis (p. 329).
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Discussion
This neatly ornamental even though small-flowered senna resembles Andean S. mandoni in foliage and pod but differs in the longer stipules and bracts, the more abruptly truncate anthers and especially in the shorter style not hooked at apex. Chilean S. cruckshanksii, although distantly allopatric in the coastal Cordillera of central Chile, is too closely similar to be other than a close genetic relative which we can distinguish only by the narrower stipules and floral bracts and a more slender style, weak and perhaps not specifically adequate characters. For comment on two related sennas sympatric with S. organensis var. organensis in Espirito Santo and Rio de Janeiro see our accounts of S. pneumatica and S. itatiaiae. The habitally similar and partly sympatric S. (ser. Corymbosae) oblongifolia is distinguished at anthesis by the infrafoliolar petiolar gland of most leaves and at least 32 (not 6-14) ovules, and later on by the narrower tumid pod and unmarked seeds turned broadside to the septa. The known populations of S. organensis as defined in the foregoing description are heteromorphic in number of leaf-stalk glands, in number, texture and venulation of the leaflets, and sometimes further in proportion of the abaxial stamens, but all retain a common facies, a characteristic perianth and, so far as known, a characteristically short but broad, piano-compressed pod of papery texture. Two variants emerge as clearly defined geographic varieties, a var. organensis in Rio de Janeiro and adjoining Minas Gerais and Espirito Santo which is replaced on Serra do Mar in Parana by var. extratropica. With these relatively well documented entities we associate, under the provisional title of var. heterandra and var. friburgensis, two peculiar sennas from within the range of var. organensis. The pod of neither is known and their taxonomic status will require reappraisal as and when new data permit.