Senna sulfurea

Title

Senna sulfurea

Authors

Howard S. Irwin, Rupert C. Barneby

Scientific Name

Senna sulfurea (Collad.) H.S.Irwin & Barneby

Description

1.  Senna sulfurea (Colladon) Irwin & Barneby, comb nov. Cassia sulfurea DeCandolle ex Colladon, Hist. Casses 84. 1816.—"Hanc Prof. de Candolle descripsit florentem mense novembri anni 1803 in horto Parisino."—No typus found at G, MPU, or P, but the plant in G-DC labelled ‘Cassia sulfurea Ile de France ou de Bourbon, Museum de Paris, 1821’ is considered authentic.—Recognized by DeCandolle himself, 1825, p. 495, as conspecific with Wellia tagera Rheede.

Cassia glauca Lamarck, Encycl. Meth. 1: 647. 1785.—". . . dans les environs de Pondichery [s.-e. peninsular India]. M. Sonnerat nous en a communique des morceaux charges de fleurs & de jeunes fruits."—Holotypus, P-LAMK!—Equated by Lamarck with Wellia tagera Rheede, 1686, l.c. infra.—Non Senna glauca Roxburgh, 1832, quae = Cassia timorensis DC.

Cassia arborescens Vahl, Symb. bot. 3: 56. 1794.—"Habitat in India orientali. KONIG."— Holotypus, labelled (verso) "Cassia arborescens. Ind. Orient. Wellia tagera Hort. Malab.," C (hb. Vahl.)!—Equated by Bentham, 1871, p. 555, with C. glauca, and by Vahl himself with Wellia tagera Rheede, 1686, q.v. infra.—Senna arborescens (Vahl) Roxburgh, Fl. Indica 2: 345. 1832, nom. illegit.—Non Cassia arborescens P. Miller, 1768, quae = Senna atomaria nob.

Cassia enneaphylla Konig ex Wight & Arnott, Prod. Fl. Pen. Ind. 1: 289. 1834, pro syn.

Cassia petropolitana Glaziou, 1905, p. 161, nom. nud.—"Petropolis . . . au Alto Serra, Rio [de] Jan[eiro, Brazil], no. 10684."—Spm. authent., Glaziou 10684, K = IPA Neg. 1167, P!- Equated with C. glauca by Harms in Fedde, Repert. Sp. Nov. 20: 124. 1924.

Wellia tagera Rheede, Hort. Ind. Malabar. 6: 17, t. 9 (fl), 10 (fr, ambae optimae!). 1686.—Equated with Cassia glauca by Hasskarl, Hort. Malabar, clav. locupletiss. 47. 1867, and all other commentators.

Flos flavus Rumphius, Herb. Amboin. 4: 63, t. 23 (mediocris). 1743.—Identified by Merrill, Herb. Amboin. 258. 1917.

Cassia planisiliqua sensu N. L. Burman, Fl. Ind. 96. 1768, quoad descr., exclus. basionym. C. planisiliqua Linnaeus quae = Senna occidentalis (Linnaeus) Link.—Spm. authent.: Cassia planisiliqua. Juxta Malayenses Cambang cuning ... a Rumphio vocata Flos flavus, G (hb. Burman.)!—Strangely equated by Index Kewensis with Albizzia lebbek.—Psilorhegma planisiliqua sensu Britton & Rose, 1930, p. 255; Little, Woodbury & Wadsworth, Trees Pto. Rico, Second Vol., fig. 372. 1974.

Cassia surattensis sensu De Wit, 1955, p. 269; Isely, 1975, p. 129 (var. surattensis), map 58 (cult, in Florida), p. 209; K. & S. Larsen, J. Nat. Hist. Siam. Soc. 25(3-4): 205. 1974; Saldanha & Nicolson, Fl. Hassan distr. Karnataka 221, 1976; Srivastava, Fl. Gorakhpur. 120. 1976; V. Singh, Bull. Bot. Surv. India 18(1-4): 90. ("1976") 1979.

Cassia glauca sensu Colladon, 1816, p. 102; DeCandolle, 1825, p. 495; Wight & Arnott, Prod. Fl. Pen. Ind. Or. 1: 289. 1834; Vogel, 1837, p. 26; Gagnepain in Lecomte, Fl. Gen. de l’lndochine 2(2): 159. 1913; Fawcett & Rendle, 1920, p. 110; Ridley, Fl. Malay Pen 1- 616 1922.

Amply leafy arborescent shrubs at anthesis 2-6 m, appearing glabrous, but the young stems, lf-stalks and axes of inflorescence strigulose with fine straight appressed hairs up to 0.15-0.3 mm, the thin-textured lfts notably bicolored, above dull dark green brunnescent when dry and glabrous, beneath pallid or glaucous and glabrous or nearly so except for puberulent midrib, sometimes sparsely ciliolate, the corymbiform racemes of large handsome fls at first axillary and lateral but commonly paniculate distally, immersed in or shortly exserted from foliage.

Stipules firmly herbaceous, falcately ascending, linear attenuate at both ends (3-)6-15 x 0.6-1.3 mm, dorsally 1-nerved, deciduous before the lf.

Lvs 14-30 cm; petiole 3-5.5(-6.5) cm, at middle 1-2.5 mm diam, subterete except for the broad shallow ventral sulcus; rachis (4-)5-15 cm, its longer interfoliolar segments 1.3-3.3 cm; glands between (1-)2-4 proximal (never between distal) pairs, stoutly stipitate, in profile 1.5-2.6 mm tall, the ovoid or ovoid-ellipsoid acute or obtuse body 0.6-1 mm diam; pulvinules 2.5-5 mm, densely pubescent; lfts 4-6(-7) pairs, accrescent distally, in outline subsymmetrically broadly elliptic, ovate- or obovate-elliptic obtuse mucronulate or minutely emarginate, the longest (distal or penultimate) pair (4-)4.5-8.5 x 2-3.8 cm, 2-2.7 times as long as wide, the tapering midrib cariniform beneath, the 7-11 pairs of fine camptodrome with intercalary secondary nerves and delicate reticulum discolored and sometimes subprominulous beneath, essentially immersed above.

Peduncles stout ascending 3-9(-13) cm; racemes 3-45 (commonly 7-15)-fld, the several simultaneously expanded fls raised beyond succeeding buds, the scarcely elongating axis becoming 1-6 cm; bracts early reflexed, thinly herbaceous ovate- triangular or broadly lanceolate (2-)2.5-8 x 1.5-3 mm, persistent into anthesis, then dry deciduous, the proximal ones (sometimes all) subtended on one side by a stipitate gland resembling those of lf-stalk; pedicels at and after anthesis 2.2-4.2 cm; fl-buds nodding when young, subglobose glabrous or basally puberulent; sepals thinly herbaceous, pale green or commonly reddish-brown with pale sub- membranous replicate margins, strongly graduated, the outermost one broadly ovate 3-5.5 mm, the innermost suborbicular (elliptic-obovate) obtuse 8-11.5 mm; corolla zygomorphic, the bright yellow petals drying orange- or pinkish-brown, dorsally puberulent along veins, nearly isomorphic, beyond the slender claw broadly ovate or oblong-obovate (2-)2.3-3 cm; androecium functionally 10-mer- ous, the stamens alike except slightly accrescent toward abaxial side of fl, the filaments of 7 adaxial ones 0-1.5 mm, of 2 latero-abaxial (0-) 1-2.5 mm, of the centric abaxial one 2-5 mm, the anthers all slenderly lanceolate in outline, straight except for slightly porrect conical tip, firm brown glabrous, dorsoventrally sulcate, ridged laterally by the prominulous sutures, (1.5-) 1.6-2 mm wide, the centric abaxial anther 6-7.7 mm, the rest 4.8-6.8 mm, all alike dehiscent apically by short lateral slits; ovary strigulose, the pistil early glabrate; style filiform, erect except at gently incurved conic tip, 4-6.5 mm, just below the minute terminal stigmatic cavity 0.2-0.35 mm diam; ovules 23-32.

Pod obliquely pendulous, the stipe 1-2 cm, the broadly linear piano-compressed body when fully fertile 12-17 x 1.3-1.8 cm, straight or slightly decurved, 2-car- inate by the slender, shallowly undulate sutures, the papery valves fuscous-brown often paler along the edges, obscurely elevated over ripe seeds, narrowly septif- erous between them, the 1-seriate locules 4.5-6 mm long extending the width of the cavity; seeds transverse, compressed parallel to the valves, oblong-elliptic in profile ±6.3-7 x 3.5-4 mm, the smooth testa lustrous castaneous, the narrowly oblong-elliptic areole ±4.5-5 x 1.2-1.5 mm.—Collections: 34.

Native to tropical India and Burma, from remote times cultivated for shade and ornament and thereby widely dispersed through Indomalaysia, becoming naturalized in disturbed forest, in hedges and waste places, long established on Mauritius (prior to 1835) and in the West Indies (Bahamas, Cuba, Jamaica prior to 1814, Martinique, Montserrat, Barbados), and locally in s.-e. Brazil (Sa. dos Orgaos, Rio de Janeiro). The genuine native range in continental Asia is obscure to us and its secondary dispersal is clouded in the literature by taxonomic confusion with closely related S. surattensis; reports from Fiji and New Hebrides are based on S. gaudichaudii (H. & A.) Irwin & Barneby.⁴

We here follow Britton & Rose (1930) and agree with V. Singh (1979, l.c.) in maintaining two specific taxa segregated from the heterogeneous concept of Cassia glauca defined in Bentham’s revision (1871). In Flora Australiensis (1864) Bentham had accepted a C. suffruticosa (our Senna surattensis) distinct from C. glauca sens. str. (our S. sulfurea), but later found it impossible to sort his Indian material even into two varieties. Primary or exclusive emphasis on size of leaflets and glaucescence of their dorsal face would lead anyone to the same conclusion, for in these respects both species are variable and appear fully confluent. On the other hand we have found that the relatively small and slightly more numerous leaflets traditionally attributed to S. surattensis (C. suffruticosa) are consistently associated with a small brachystylous flower that gives rise to a shorter, narrower, more shortly stipitate pod. Like us, Isely (1975, l.c.) has seen two taxa in the complex, which he evaluates as varieties of Cassia surattensis, mentioning in support of them chromosome counts by Pantulu (1960) which suggest that S. surattensis (n = 28) is a tetraploid derivative of diploid S. sulfurea (n = 14), perhaps not known in a genuinely wild state. We have not seen vouchers for these counts, however, which will require careful checking because of the taxonomic and nomenclatural confusion that has followed Bentham‘s comprehensive definition of C. glauca, a confusion which has contaminated the literature of the past century and has left the exact native range of each segregate species still to be defined. This problem is, however, peripheral to our present purpose.

Senna surattensis and S. sulfurea are the only two genuine sennas with ten fertile stamens encountered outside gardens in the New World, and are thus readily identified to section when in flower. In fruit they become somewhat generalized sennas without striking individuality except for the glaucescent foliage and the stipitate gland, unfortunately not reliably present in all plants, that subtends the proximal floral bracts of the raceme. In the West Indies, where the question is most likely to arise, they will be recognized in fruit by the combination of ample obtuse leaflets and relatively broad piano-compressed pod shallowly undulate along the sutures.

Roots, bark and leaves of Cassia glauca auct., probably meaning our Senna sulfurea, enter into folk medicines of India and Indomalaya prescribed for treatment of gonorrhea, gout, diabetes and arthritis, and the flower-buds are eaten in salad. Both S. surattensis and S. sulfurea are cultivated primarily for shade and ornament, being prized for rapid growth and prolific flowering over long successive periods but furnishing at best a soft and perishable wood.

Particular attention must be drawn to our changed interpretation of Cassia surattensis, which runs contrary to modern practice. De Wit (1955, p. 269) applied the epithet surattensis erroneously to the species with larger flower and fewer ample leaflets, our S. sulfurea, a mistake that might have been avoided by closer analysis of the protologue, which describes the leaflets as eight pairs. Burman simultaneously described C. surattensis sensu De Wit, recognized as the Flos flavus of Rumphius, under the name Cassia planisiliqua, a Linnaean binomial technically synonymous with S. occidentalis (Linnaeus) Link. While the epithet surattensis must be adopted for the species known latterly as Cassia suffruticosa, the earliest epithet available and legitimate in Senna for the related, large-flowered species is apparently sulfurea. Cassia discolor Desvaux, which has a short priority over C. sulfurea, has been considered a synonym (Bentham, 1871), but is based on a mixture of foliage of S. pallida and mismatched fruit of S. sulfurea, and herein is typified by the "discolorous" foliar element of the typus. The true identity of C. surattensis was first appreciated, according to annotation of the holotypus at Geneva, by Drs. K. and S. Larsen in 1978.