Senna pendula var. tenuifolia

  • Title

    Senna pendula var. tenuifolia

  • Authors

    Howard S. Irwin, Rupert C. Barneby

  • Scientific Name

    Senna pendula var. tenuifolia (Benth.) H.S.Irwin & Barneby

  • Description

    126p. Senna pendula (Willdenow) var. tenuifolia (Bentham) Irwin & Barneby, comb. nov. Cassia bicapsularis var. (y) tenuifolia Bentham in Martius, Fl. Bras. 15(2): 107. 1870.—. . prope Ilheus: Luschnath (Mart. Herb. Fl. Bras. n. 715.); ad fl Amazonum: Spruce n. 1701. (distributa sub nomine C. biflorae aff.)."—Lectoholotypus, collected at Mana- quirigapo near mouth of R. Solimoes, Amazonas, Brazil, VI.51 (fl), Spruce 1701, K (hb. Hook.)! isotypi, K (hb. Benth.), M! paratypus, Martius Hb. 715, BR! = S. pendula var. glabrata.

    Weakly shrubs, potentially vinelike or arborescent, at anthesis 2-7 m, the trunks sometimes deeply immersed by floodwaters; petiolar gland 1; lfts membranous (2-)3-4(-5) pairs, the distal pair elliptic or broadly oblanceolate 2.7-5 x 1-2 cm, the camptodrome secondary veins ±10-13 pairs, tertiary venulation weak erratic, the blade thinly pilosulous dorsally with straight ascending hairs up to 0.6-1 mm, or the vesture confined to anterior basal angle of midrib, or lacking; longest sepal 13-15 mm; longest petal 18-24 mm; blade of staminodes narrowly oblong-oblanceolate 3.4-4.5 x 1-1.3 mm; 2 long abaxial filaments 10.5-12 mm, their anther 9-11 x 1.5-2 mm, the drum-shaped beak very short or scarcely differentiated; ovary thinly pilosulous or glabrous; style 2.5-3 mm; ovules 100-152; body of pod 19-29 x ±1 cm, unknown when quite mature, when green either terete or deeply constricted between seeds, the septa then much narrower than the locules, and the pod resembling a double row of beads.—Collections: 10.

    Flooded river banks and margins of varzea forest below 250 m, discontinuously widespread in Brazilian Amazonia, along the Great River from the mouth of the Jari in Para upstream nearly to the Peruvian border in Amazonas, s. through the Araguaia-Tocantins and Madeira-Guapore basins into n. Goias and Rondonia.— FL IV-VIII.

    The characters listed in our diagnosis, namely a solitary petiolar gland, an ample perianth, an abaxial pair of filaments hardly longer than their stout brown anther, elongate and narrow staminodes, a short style and an extremely long pod form a distinctive syndrome coinciding with a riparian habitat in high Amazonian forest. Length of pod requires confirmation for populations from which we have only flowering material, but this has a consistently high number of ovules appropriate to an elongate fruit. The pod of Krukoff 4525 from Tefe, though not fully ripe, is clearly of the cylindric type common in S. pendula, which has interseminal septa extending (in double file) across the width of the cavity and this, so far as known, is the pod to be expected normally in var. amazonum. With some hesitation we include in the variety two collections from the upper Madeira-Guapore basin (Prance 5303; Black 15157, both NY) and one from the Araguaia basin in northern Goias (Pires & Santos 16669, NY) in which the septa fail to develop normally, with the consequence that the valves become deeply constricted between seeds and the whole pod doubly moniliform. Whether this pod is pathogenic or belongs to a distinct race we cannot determine.

    In our key to the varieties of S. pendula we have incidentally characterized two shadowy sennas which have many morphological characters in common with var. tenuifolia and share its riparian habitat in Amazonia but which are so poorly known that we pass over them with brief notice but no formal description.