Senna mucronifera

  • Title

    Senna mucronifera

  • Authors

    Howard S. Irwin, Rupert C. Barneby

  • Scientific Name

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

  • Description

    66.  Senna mucronifera (Bentham) Irwin & Barneby, comb. nov. Cassia mucronifera Martius ex Bentham in Martius, Fl. Bras. 15(2): 116. 1807.— ". . . ad ripas fluminis S. Francisco prope Malhada [at mouth of R. Carinhanha, on Minas Gerais boundary] prov. Bahiens: Martius; inter Lavrinha et Rio Maranhao prov. Goyaz: Pohl; in prov. Minas Geraes: Regnell III. n. 477.; . . . Sorocaba prov. S. Paulo: Lund."—Lectoholotypus, Martius s.n., collected at Malhada in late XI. 1818 (fl.fr jun), M! = F Neg. 6247; paratypi, Pohl 1702, K! Regnell III/477, K! = IPA Neg. 960, 961, S! Lund in hb. Warming. 190, C!—Emelista mucronifera (Bentham) Pittier, J. Wash. Acad. Sci. 19: 176, comb, subnud. 1929.

    Coarse suffrutescent weakly malodorous herb with few erect or assurgent virgate, simple or distally few-branched, bluntly angulate stems at anthesis 9-24 dm, densely pilosulous throughout or almost so with rather stiff erect, ascending or loosely incurved, sometimes distally (in inflorescence) subappressed, often sordid hairs up to 0.2-0.45 mm, the foliage bicolored, the firmly membranous lfts dull dark green above, paler beneath, nearly always pubescent on both faces, the lvs abruptly or gradually diminished distally, the inflorescence an exserted thyrse or thyrsoid panicle of subsessile 1-2-fld racemes terminating the main axis and its distal branches.

    Stipules erect herbaceous, falcately linear-lanceolate (5-)6.5-15 x 0.8-2 mm, strongly carinate-nerved, deciduous before the lf.

    Lvs (disregarding depauperate distal ones) 5-13 cm; petiole including little swollen pulvinus (0.8-) 1-3.5 cm, at middle 0.8-2 mm diam, ribbed dorsally and laterally, openly shallow-sulcate ventrally; rachis 1-3.5 cm, shorter or little longer than petiole; glands always between proximal, usually between the second (of 3), less often between distal pairs, sessile or short-stipitate, in profile 1.2-3(-4) mm tall, the reddish-brown, narrowly lance-fusiform obtuse or acute body 0.3-0.8 mm diam; pulvinules (0.8-) 1-3 mm; lfts 2 or (in most larger primary cauline lvs) 3 pairs, accrescent distally, the distal pair broadly or narrowly obovate-cuneate or obovate, obtuse mucronate or deltately to subacuminulately acute, (2.6-)3-6(-6.5) x (1.2-) 1.4-3(-3.4) cm, 1.5-2.5 (commonly ±2) times as long as wide, at base cordate on proximal and cuneate on distal side, the centric straight midrib with (7-)8- 12(- 14) pairs of camptodrome secondary veins prominulous on both faces, more sharply and coarsely so beneath, there giving rise to a pronounced tertiary or reticular venulation.

    Peduncles 0-3.5 mm; racemes 1- or 2-fld, the axis 0-1.5 mm; bracts ovate- or lance-acuminate 2-3.5 mm, caducous; pedicels (at and after full anthesis) 18-42 mm; fls in attitude and form like those of C. cobanensis except a little larger; long sepals broadly obovate or oblong 12-20 mm, the nerves becoming prominent and anastomosing distally; petals either pale or orange-yellow, the longer ones 22-31 mm; androecium glabrous or the filaments sometimes puberulent, those of the 4 median stamens 1-2 mm, of 3 abaxial ones (3.5-)5-10 mm, the anthers of 4 median stamens 6-8.5 mm, their divaricate biporose beak ±0.3 mm, those of 3 abaxial ones 11-14 mm, abruptly contracted into an erect beak 1.4-3 mm, this abruptly bent forward near or beyond middle and dilated into a semicircular pollen-cup not divided by a septum; ovary strigulose; style 2.5-3 x 0.3-0.4 mm, gently incurved just below the small stigmatic cavity; ovules 44-52.

    Pod (little known) erect but slightly or strongly, either simply or sigmoidally recurved, narrowly linear ±18-25 x 2-4 mm, resembling that of S. pilifera, the seed-locules ±4-6 mm long; seeds narrowly oblong-subcylindroid ±5.1-5.8 x 1.8-2.7 mm, the testa castaneous lustrous, the areole linear 4.0-5.2 x 0.5-0.8 mm.—Collections: 32.

    Campo, cerrado, disturbed woodland, ±300-1000 m, local, scattered over the Planalto between the s. headwaters of the Amazon in Bolivia (Santa Cruz) and Brazil (Mato Grosso and Goias), the Sao Francisco valley on the Minas-Bahia boundary, s.-e. Paraguay, and the headwaters of Rio Tiete in e. Sao Paulo—Fl. in Brazil and Bolivia (I—)III—VIII, in Paraguay XI-II, the full season probably not known.

    Senna mucronifera closely resembles some larger-flowered forms of S. cobanensis, from which it differs principally in the long narrow pod. This, in its early stages of development, when it is rapidly elongating but not yet filled out with seeds, resembles that of S. obtusifolia or S. hirsuta var. hirta, and when ripe is about twice as long but less than half as wide as that of S. cobanensis. More subtle and less consistent differential characters of S. mucronifera are the longer sepals, commonly longer petals, larger and longer-beaked abaxial anthers, more coarsely reticulate leaflets, and a more decisively exserted inflorescence. The two species are allopatric, but separated in Bolivia, so far as known at present, only by the valley of Rio Mamore, and thus are virtually vicariant in dispersal. Relationship with S. leiophylla is discussed under the next.

    In the protologue Bentham described the central abaxial stamen as sterile and much smaller than the neighboring pair, but we have not confirmed this condition in any flower examined.