Senna lechriosperma

  • Title

    Senna lechriosperma

  • Authors

    Howard S. Irwin, Rupert C. Barneby

  • Scientific Name

    Senna lechriosperma H.S.Irwin & Barneby

  • Description

    62.  Senna lechriosperma Irwin & Barneby, sp. nov., S. velutinae et S. australi arete affinis et cum iis leguminis valvulis nervo crasso submediano longitrorsus percursis congrua, foliolis latis (sed apice deltatim sub- acutis nec emarginatis) sepalisque intimis dorso glabris huic forsan propior, ab ambabus legumine latiori plano-compresso ± 9-10 (nec ± 2-5) mm lato et seminibus transversis ideoque leguminis loculis latioribus quam longioribus, his notis ab aliis seriei Laxiflorarum speciebus insigniter diversa.—BRAZIL. Pernambuco: Fazenda Experimental de Pesqueira, 23.XI. 1962 (fl,fr), J. C. Gomes 1247.—Holotypus, NY.

    Shrubs of unknown stature, except for more acute lfts resembling C. australis in general habit, apart from dorsally glabrous inner sepals rusty-pilosulous or -strigulose throughout with ascending or subappressed, straight or sinuous hairs up to 0.5-0.8 mm, the young stems, lf-stalks and axes of inflorescence densely, the bicolored foliage more thinly so, the (dry) lfts brownish, above dull or sub- lustrous, beneath paler dull, ± pilosulous on both faces, the inflorescence wholly of C. australis.

    Stipules foliaceous persistent, reflexed against stem, very obliquely incurved- semicordate 10-15 x 4-10 mm, at base dilated into a broadly obtuse descending amplexicaul auricle, at apex contracted into a slender, sometimes setiform acumen, the blades radially venulose from point of attachment, pubescent on both faces.

    Lvs 6.5-14.5 cm; petiole including little differentiated pulvinus 7-21 mm, at middle ±1-1.5 mm diam, beyond middle shallowly open-sulcate; rachis (2-)2.5-5.5 cm; glands (often eaten) between all pairs of lfts stipitate, including the usually puberulent stipe 1.5-3 mm, the ovoid acute or fusiform body 0.45-1.1 mm diam; pulvinules 2-3.5 mm, densely pilosulous; lfts (2-)3-4, in most adult lvs exactly 4 pairs, accrescent distally, the distal pair obliquely obovate or elliptic- obovate from inequilaterally rounded or subcordate base, (4-)4.5-8.5 x 2-4 cm, 1.6-2.1 times as long as wide, at apex deltate-mucronulate, the margins revolute, the centric straight or slightly incurved midrib with 9-11 pairs of major camptodrome secondary veins immersed above, strongly prominulous beneath, the tertiary connecting venules faintly prominulous on one or both faces but not forming a regular reticulum.

    Peduncles 1-2.5 cm; racemes ±15-30-fld, the axis becoming 4-10 cm; bracts early deciduous firm ovate acute to narrowly lance-subulate 2.5-4.5 mm; pedicels at and after full anthesis 2.5-4 cm, subtended laterally at base by a slenderly stipitate, narrowly fusiform gland 2-3 mm; fl-buds rusty-puberulent, at least in lower half, when young, the later-expanding inner sepals glabrous dorsally; sepals obovate-suborbicular very unequal, the outermost (abaxial) one 4-8 mm, the innermost 10-15 mm; petals and androecium of C. velutina, the abaxial petals 25-32 mm; ovary densely rusty-pilosulous-strigulose; style linear straight 5-9.5 x 0.3 mm.

    Stipe of pod ±3 mm, the linear straight or decurved body 9-15 x 0.9-1 cm, piano-compressed, bicarinate by the often undulately constricted sutures, the stiffly chartaceous livid-castaneous valves scarcely constricted over seeds, charged lengthwise with a single coarse nerve running parallel to the sutures a little displaced from center toward abaxial one, the thick but very narrow inter- seminal septa 3.5-4 mm apart, the seed-locules in consequence broader than long; seeds (few seen) horizontal to long axis of pod or very obscurely oblique, oblong- obovoid ±4.6 x 3 mm, the testa smooth brown but not highly lustrous, the areole oblong-elliptic ±3x1 mm.—Collections: 6.—Fig. 22.

    Habitat poorly known, recorded from chapada and disturbed taboleiro thickets, ±300-750 m, known from scattered stations in s.-e. Maranhao, Piauf, Ceara and Pernambuco, in e. Brazil.—Fl. IX, II, IV, VI, perhaps irregularly following rains.

    This well-marked species was independently recognized as new by the late Dr. D. Andrade-Lima, who did not live to describe it, as we had hoped. The epithet lechriosperma alludes to the transverse orientation of the seeds, in the context of the genus nothing extraordinary, but hitherto thought impossible for a member of sect. Prososperma, of which seeds turned downward along a narrow pod are the diagnostic feature. We interpret the direction taken by the seed within its locule as merely a function of the pod’s width, and feel confident that this species is a genuine member of ser. Laxiflorae with which it agrees in all details of foliage, of glands on leaf-stalf and subtending the pedicels, of perianth and androecium, and especially in the prominent cordlike nerve running the length of the pod’s valves, the hallmark of the Laxiflorae pod.

    The earliest collection of this senna known to us is Gardner 2124 (BM), collected in southern Piaui early in 1839. The specimens, in young flower, are unusual in having only two or three pairs of leaflets to the leaf, but seem otherwise a good match for the plants from Pernambuco. We surmise that the Cassia velutina reported from Ceara by Fernandes & Bezerra (XXIII Cong. Nac. de Bot., Belo Horizonte, 1.1977) is actually this species.