Senna alexandrina Mill.

Authors

Howard S. Irwin, Rupert C. Barneby

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 2: 455-918.

Family

Caesalpiniaceae

Scientific Name

Senna alexandrina Mill.

Type

No typus seen. The name S. alexandrina, unaccountably overlooked by Bentham (1871), has since Colladon (1816, p. 94) been equated with Cassia senna a Linnaeus, C. lanceolata Forsk. and C. acutifolia Delile, while the specific epithet is the earliest avail

Synonyms

Cassia senna L., Cassia acutifolia Delile, Cassia angustifolia Vahl, Senna angustifolia (Vahl) Batka

Description

Species Description - Ours erect-ascending, precociously flowering, ultimately suffrutescent herbs at anthesis 3-10 (in Paleotropics potentially -30) dm, sparsely strigulose with fine, truly appressed straight hairs up to 0.15-0.3 mm, the foliage pallidly olivaceous, concolorous or yellowish above, the axillary and finally subterminal loose racemes surpassing their lf. Stipules ascending or spreading lance-subulate 1.5-3 mm, at base dilated on side further from petiole, there ±1 mm wide, early dry deciduous. Lvs 5-16 cm; petiole including wrinkled but not much dilated pulvinus 1-2.5 cm, at middle 0.5-1.2 mm diam, shallowly sulcate ventrally; rachis (2.5-)3-13 cm; petiolar glands 0 (but spicules present between lfts); pulvinules ±1 mm; lfts (3-)4-8 pairs, ± accrescent distally, in outline lanceolate acuminulate or acute mucronulate, the longest (distal or penultimate) ±2.5-5 x 0.5-1 cm, 4-7 times as long as wide, at base subsymmetrically cuneate, the margin plane, the midrib and 3-5(-6) pairs of narrowly ascending secondary veins prominulous on both faces, an open irregular tertiary venulation raised or not. Racemes (7-)10-30-fld, the fl-buds elevated well beyond the 2-4 simultaneously open flowers, the elongating axis together with peduncle becoming 1-2 dm; bracts membranous or membranous-margined, yellowish or fuscous, obovate 5-7 x 4.5-6 mm, at base shortly auriculate on both sides, enveloping the young fl-buds, cast off as the pedicel elongates; pedicels at and after anthesis 1-2(-2.5) mm, surmounted by a narrowly funnelform hypanthium 2.5-4 mm (easily and often in the past mistaken for part of pedicel); fl-buds ascending, obliquely obovoid or semi-obovoid obtuse; sepals submembranous fuscous or yellowish pallid-margined, glabrous or microscopically papillose-puberulent, in outline obovate or oblong- oblanceolate and of subequal length ±9-11 mm; petals glabrous yellow or orange- yellow drying stramineous or whitish brown-veined, in outline obovate or oblong- obovate beyond the short claw, ±13.5-15 mm; androecium glabrous, the 3 adaxial members minute or sterile (anthers 1.1-2 mm), the filaments of 4 median ones 2-2.6 mm, of 2 latero-abaxial ones 2.2-2.5 mm, of the centric abaxial one 3.5-4 mm, the anthers of 4 median and the centric abaxial one 3.3—4.3 mm, straight or almost so, of the 2 latero-abaxial lunately incurved, narrowly lance-attenuate 9.5-10 x 1.3-1.5 mm, at base inequilaterally sagittate, all 7 fertile anthers at truncate apex bluntly 2-umbonate on ventral side and 2-porose on dorsal one; ovary densely strigulose; style glabrous linear-filiform, evenly incurved from base, sometimes a trifle thickened distally, at or just below the obliquely terminal stigmatic cavity 0.2-0.25 mm diam; ovules 6-10. Pod spreading or declined stipitate, the true stipe (beyond orifice of hypanthium) 2.5-3 mm, the broadly oblong or oblong-elliptic, straight or gently incurved, piano-compressed body with us 4-5.5 x 1.6-1.7 (in paleotropic races potentially up to 7 x 2.6) cm, rounded at both ends and at base abruptly cuneately contracted into stipe, the style-base becoming infraterminal, the thinly papery dull or moderately lustrous valves livid-brown becoming paler along the slender sutures, slightly elevated but not longitudinally crested over ripe seeds, the cavity dilated only along middle and there narrowly but completely membranous-septate; dehiscence inert but complete, along both sutures: seeds compressed parallel to the valves, in outline oblong-paddle-shaped, at apex truncate-emarginate, 5.2-6.2 x 3-3.6 mm, the ivory-stramineous testa sharply elaborately sinuous-rugulose overall, the oblanceolate areole 1.5-2.4 x 0.4-0.5 mm engraved into a vertical ridge at proximal end of seed; n = 14 (?13).—Collections: 30 (4 neotropical).—Fig. 10 (androecium), 13 (pod, seed), both under synonym angustifolia.

Distribution and Ecology - Waysides and waste places in the lowlands, adventive and naturalized in Hispaniola (s.-centr. Dominican Republic and Haiti) and in the Balsas valley in s. Mexico, cultivated and possibly casual elsewhere in the New World; native of grasslands and deserts of Tropical Africa mostly n. of the Equator, extending e. through Near East to the plains of peninsular India.—Fl. in the West Indies year around.

Discussion

The exareolate seed illustrated as that of Cassia angustifolia by Malick & Krishna, 1978, fig. 1, is certainly misidentified.

Common Names

True senna, Alexandrian s., Tinnevelly s., sen de Espana

Distribution

West Indies| West Indies| India Asia| Mexico North America|