Senna trachypus

  • Title

    Senna trachypus

  • Authors

    Howard S. Irwin, Rupert C. Barneby

  • Scientific Name

    Senna trachypus (Benth.) H.S.Irwin & Barneby

  • Description

    165.  Senna trachypus (Bentham) Irwin & Barneby, comb. nov. Cassia trachypus Bentham in Martius, Fl. Bras. 15(2): 122. 1870, sens, restr., exclus. C. trachypode Mart, in herb.—"Habitat in silvis humidis prope Craton prov. Ceara: Gardner n. 1575; in collibus circa Oeiras prov. Piauhy frequens: Gardner n. 2119; in sepibus silvarumque marginibus prov. Minas Geraes: Martius; ad S. Carlos prov. S. Paulo: Patricio da Silva Manso (Mart. Herb. Fl. Bras. n. 1072.)."—Lectotypus, Gardner 2119, collected V.1829 (fl, fr), K (hb. Hook.)! = IPA Neg. 983; isotypi, BM, F, FI, K (hb. Benth.), NY (hb. Meissner.), W! paratypi conspecifici, Gardner 1575, BM, K, W! The paratypi Martius sn ex Minas Gerais, BR! and Silva Manso 269 distrib. Martius. Herb. 1072, †B = F Neg. 1758, BR, K = NY Neg. 1463, NY! represent respectively S. acuruensis var. interjecta and S. multijuga var. lindleyana.

    Cassia trachypus sensu Bentham, 1871, p. 546, exclus. loc. S. Paulo et Minas Gerais.

    Arborescent shrubs at anthesis 1.5-4 m, with slender, densely leafy reddish- brown annotinous branchlets, these with all lf-stalks and axes of inflorescence at once finely minutely villosulous with filiform incurved whitish hairs and viscidly setulose with orange or yellow peg- or tack-shaped setules up to 0.1-0.2 mm, the thinly chartaceous, notably bicolored lfts glabrous on both faces, above dark dull green brunnescent when dry and pallidly venulose, beneath pallidly olivaceous- glaucescent, the inflorescence composed of axillary simple racemes immersed in or distally exserted from foliage.

    Stipules erect setiform 2-5.5 cm caducous, lacking from fruiting spms.

    Lvs (4.5-)6-16(-18) cm; petiole including moderately dilated firm pulvinus (1.5-)2-4.5(-5) cm, at middle 0.4-0.8 mm, rounded dorsally, very shallowly sulcate ventrally; rachis (1.5-)2-8.5(-10) cm; petiolar glands between 2 proximal or commonly (diminishing distally) between all pairs of lfts stipitate, the lowest in profile 1.3-2.5 mm, the body slenderly ovoid-fusiform acute 0.2-0.6 mm diam glabrous; lfts 5-9 pairs, moderately accrescent upward, ascending from rachis face upward on pulvinule 0.8-1.6 mm, in outline obovate or oblance-obovate obtuse or subtruncate, mucronulate by the excurrent midrib, the distal pair (16-)20-42 x 8-21 mm, 1.6-2.5 times as long as wide, at asymmetric base rounded on proximal and cuneate on distal side, the margin plane, the centric straight midrib with 5-8 pairs of major camptodrome and intercalary secondary veins finely prominulous above, sharply so beneath, a tertiary reticulation commonly visible but immersed above, finely but evidently raised beneath.

    Peduncles 1.5-4 cm; racemes loosely (2-)4-12(-18)-fld, the axis becoming (0.2-)l-6(-8) cm; bracts obovate cymbiform ±1.5-2 mm, early dry and caducous from below young fl-buds as pedicels elongate; pedicels 2.3-3.7 cm, glandless at base; buds obovoid obtuse glabrous or almost so; sepals brownish pale-margined, faintly several-nerved from base, strongly graduated, the outermost scarcely Vi as long as inner ones, these ovate- or obovate-suborbicular very obtuse concave 10-13 mm; petals golden-yellow glabrous, resembling those of S. pallida in outline and asymmetry, the obliquely reniform abaxial one longest, 2.5-3.4 mm; androecium glabrous, the filaments of 4 median stamens 1.5-2.8 mm, of one abaxial one 2-3.5 mm, of the one exactly abaxial and of one contiguous to it 4-9.5 mm, the anthers of 4 median stamens little curved, the body 5.2-6.5 mm, the divaricate biporose beak scarcely 0.5 mm, the anthers of 3 abaxial ones more strongly incurved, the body 5.5-9 mm, contracted into an erect tubular beak 2-3 mm, the orifice 1-porose or divided by filiform septum; ovary glabrous, the stout, gently incurved style 1.5-2 mm, not dilated distally, ±0.5 mm diam; ovules 44-50.

    Pod pendulous, the stipe 5-8 mm dilated upward, the body linear-oblong straight or almost so, strongly compressed, 7.5-11 x 1.1-1.6 cm, the papery brunnescent or nigrescent valves flat or obscurely colliculate down the middle, finely transverse-venulose, dull or sublustrous in age, the sutures narrowly sharpwinged, the ventral wing ±0.8-1 mm wide; seeds linear-oblong, obtusely 4-an- gular 5.4-6.5 x 1.1-1.6 mm, grooved on each side, the testa pale brown dull crackled, the faces marked with a linear-elliptic areole 1.1-1.6 x 0.25-0.4 mm.— Collections: 18.—Fig. 31.

    Seasonally dry woodlands (caatinga, cerradao), 100-370 m, locally plentiful over Atlantic n.-e. Brazil n. of Rio Sao Francisco, from the Parafba valley in s.- centr. Maranhao to n.-centr. and s. Ceara and w. Parafba and Pernambuco.—Fl. Ill-VI(-XI), the empty pods sometimes long-persistent.

    A handsomely floriferous senna, notable for the combination of strongly bicolored, pale-venulose foliage, viscid-setulose leaf-stalks and inflorescence, beaked abaxial anthers and linear seeds, a syndrome repeated in northeastern Brazil only by the southwardly vicariant S. acuruensis. The latter is very closely related, differing ultimately only in the bluntly three-nerved, not acutely narrowwinged sutures of the pod but further from var. acuruensis, found immediately south of Rio S. Francisco, in the fewer and larger leaflets and from geographically more distant S. acuruensis var. catingae, which has almost the same foliage, in the presence of viscid setules throughout the inflorescence as well as on the petioles. Superficially similar Brazilian S. rostrata and S. aversiflora lack viscid setules entirely and differ in their umbellately 2-3-flowered racemes and in the stalked glands subtending the pedicels.

    Our concept of S. trachypus is materially narrower than that of Bentham, who included in the protologue of Cassia trachypus an element of S. multijuga var. lindleyana in the shape of Martius Herbarium No. 1072 collected in Sao Paulo by Silva Manso. This collection, of which two likenesses have been distributed (see above) as phototypes of C. trachypus, disagrees with the protologue in its glandless foliage and inflorescence and could have suggested neither Bentham’s diagnosis ("racemis . . . viscido-puberulis") nor the epithet attributed to Martius, apposite only to the plants with scabrously setulose pedicels. The specimens from which Bentham derived the epithet trachypus are also not conspecific with the lectotypus of C. trachypus but represent the related and, at anthesis, deceptively similar S. acuruensis var. interjecta.