Senna smithiana

  • Title

    Senna smithiana

  • Authors

    Howard S. Irwin, Rupert C. Barneby

  • Scientific Name

    Senna smithiana (Britton & Rose ex Britton & Killip) H.S.Irwin & Barneby

  • Description

    15.  Senna smithiana (Britton & Killip) Irwin & Barneby, comb. nov. Chamaefistula smithiana Britton & Rose ex Britton & Killip, Ann. N.Y. Acad. Sci. 35: 172. 1936.—"Santa Marta, Colombia. Type from five miles east of Cienega, September 10, 1898, H. H. Smith 251, type (NY), 250."—Holotypus, NY! isotypi, F, MICH, US; paratypi (250, from Bonda), BR, K, NY, USF!

    Fruticose and ultimately arborescent, at anthesis 2-4(-?) m, with habit, stipules and foliage of S. oxyphylla var. oxyphylla but never pilosulous, the plane-margined lfts strigulose with appressed hairs 0.2-0.4 mm, sometimes glabrate above, the primary axis of the terminal, shortly exserted panicle abruptly zigzag.

    Stipules falcately linear-oblanceolate 0.8-2 mm wide.

    Lvs 9-15 cm; petiole 15-35 mm, at middle 0.9-1.3 mm; rachis 14-23 mm, as long or commonly a little shorter than petiole; gland between proximal pair of lfts sessile or substipitate, 2-3 x 0.7-1.4 mm glabrous; distal pair of lfts obliquely ovate- or ovate-elliptic-acuminate 6.5-9.5 x 2-4.5 cm, 2-3 times as long as wide, the venation as in S. oxyphylla; proximal pair obliquely ovate-acuminate 1/2-2/3 as long, proportionately broader but not strongly cordate-dilated on proximal side at base.

    Pedicels 16-33 mm; buds globose glabrous or almost so; sepals membranous strongly graduated, the inner broadly ovate-orbicular 7-10 mm, the outermost scarcely more than 1/2 as long; petals variably heteromorphic, the longest 16-24 mm; androecium functionally 6- rarely 7-merous (one abaxial stamen commonly lacking), the anthers as in S. oxyphylla, of 4 median stamens 5.5-8 mm with beak 0.5 mm, of 2 (or 3) abaxial ones 2-5 mm, with porrect biporose beak 1.3-1.8 mm; ovary of S. oxyphylla, the ovules 108-198.

    Pod and seeds unknown.—Collections: 5.

    Forest and thickets in disturbed forest, 10-350 m, local, known only from foothills of Sa. Nevada de Santa Marta in n. Magdalena, Colombia, and of Sa. de Perija in adjacent Zulia, Venezuela.—Fl. IX-XII.

    A species ambiguously poised between S. bacillaris, of which it has almost the calyx and large flower together with the plane leaflets, and S. oxyphylla, similar in size and form of foliage but small-flowered and with revolute leaflets. The loss of one adaxial stamen in most flowers sets S. smithiana apart, but this same stamen is much reduced in size in S. bacillaris var. benthamiana and its full suppression provides only a weak specific character. Possibly S. smithiana is merely a local variety of S. bacillaris or conceivably a set of populations derived from a S. bacillaris × oxyphylla hybrid, entirely plausible so far as geographical dispersal is concerned. The pods of S. bacillaris and S. oxyphylla are much alike in external form, but the seeds are different, those of the former being distinguished by an emphatic areole. Until seeds of S. smithiana become known, the affinities of the species cannot be assessed with any expectancy of finality.