Senna trianae

  • Title

    Senna trianae

  • Authors

    Howard S. Irwin, Rupert C. Barneby

  • Scientific Name

    Senna trianae H.S.Irwin & Barneby

  • Description

    31.  Senna trianae Irwin & Barneby, sp. nov., foliis mediocribus, habitu toto cum inflorescentia S. undulatae ut videtur proxima sed stipulis angustis- sime linearibus, foliolis concoloribus, bracteis parvis deciduis 1.53.5 x 1 (nec ±4-20 x 2-7) mm, pedicellis abbreviatis 5-16 (nec 15-30) mm, forsan ulterius legumine gracili ±8-10 x 0.7 cm diversa.—COLOMBIA. Cundinamarca: 14 km w.-n.-w. of Melgar, 330 m, 8.1.1974 (fr), G. Davidse 5799.—Holotypus, MO; clastotypus (fragm), NY.— Above Rio Sumapaz, 14 km w. of Melgar, 400 m, 13.1.1974 (fl jun), A. Gentry et al. 9200.—Paratypus, MO.

    Shrubs ±lm with stiff terete annotinous and obtusely angulate hornotinous branchlets, minutely puberulent with forwardly subappressed hairs up to 0.1-0.2 mm, the foliage concolorous, the stiffly chartaceous lfts dull yellowish-olivaceous and remotely puberulent or glabrate on both faces or glabrous above, the inflorescence of short crowded racemes either leafy-bracteate or leafless and terminal, not or only shortly exserted.

    Stipules erect firm linear-lanceolate 3-5 x 0.4-0.6 mm, deciduous before the lf.

    Lvs 7-21 cm; petiole including the dilated wrinkled pulvinus 1.3-5 cm, at middle 0.7-1.4 mm diam, obtusely ribbed dorso-laterally and openly shallow-sulcate ventrally; rachis 1-3 cm, usually shorter than petiole; glands between each pair of lfts, sessile or short-stipitate 1.5-3.5 mm tall, the ovoid or ellipsoid obtuse or acute body 0.4-0.9 mm diam; distal pair of lfts obliquely ovate- or broadly lance- elliptic, shortly and obtusely acuminate (4-)5-13.5 x (1.5-)2-4.7 cm, ±2.3-3 times as long as wide, at base inequilaterally rounded on both sides, the margin plane or obscurely revolute, the incurved midrib with (6-)7-13 pairs of camptodrome secondary and connecting tertiary veins all bluntly prominulous above and more sharply elevated beneath, the reticular venulation above immersed, beneath prominulous and elaborated into defined areoles ±0.5 mm diam; proximal pair of lfts ±0.5-0.7 times as long as the distal, proportionately only a trifle broader.

    Racemes closely ±3-10-fld, the axis including short peduncle 0.5-4 cm; bracts firm, ovate-elliptic or lance-subulate concave 1.5-4 x 1-16 mm, deciduous by full anthesis; pedicels 5-16(-22) mm; buds globose, gray- or yellowish-strigulose; sepals little graduated, firm with yellowish submembranous margins, broadly obovate to oblong-obovate obtuse 5-7.5 mm; petals (little known) of ser. Bacillares but very short-clawed, the blade suborbicular, the longest 11-14 mm; functional stamens 7(-8), the puberulent filaments of 4 median stamens 1.2-2 mm, of 3 abaxial ones 2-5 mm, the 4 median anthers slightly incurved 4.5-6 mm, with very short divaricate 2-porose beak 0.3-0.5 mm, the abaxial scarcely different (3.6-)4-6 mm with slightly longer beak 0.4-0.6 mm, the 3 adaxial stamens either minute staminodal or variably developed into effete (or one into functional) anthers; ovary densely puberulent, the dilated stigma ±1.2 mm diam; ovules ±100.

    Pod pendulous, the stipe ±2-3 mm, the body linear-cylindroid 8-10 x 0.7 cm, the sutures ±2 mm wide without obvious thickened border, the firmly chartaceous brown valves becoming coarsely transverse-reticulate-venulose, the dehiscence follicular; seeds (not seen) 2-seriate, embedded in pulp.—Collections: 8.

    Dry rocky slopes and probably in thickets or at margin of forest, 300-1300 m, local, known only from the Magdalena valley in Cundinamarca and n. Tolima, Colombia.—Fl. (?) I—III.

    Collected twice by Triana over a century ago (1851-7) and several times in recent years, this seems to be a local derivative of the S. undulata-S. quinquangulata complex, of which it has the biglandular leaf-stalk and small flower. It differs from both S. undulata and S. quinquangulata in the setiform stipules, the concolorous, scarcely revolute leaflets and small slender pod; and further from S. undulata, which it resembles in leaf-size, in the small caducous bracts. It resembles S. viminea in the stipules, but that, at least outside Jamaica, has only one petiolar gland, and in its scattered continental range a more ample flower, very markedly bicolored leaflets and a proportionately broader pod. The range of S. undulata has been traced south in Colombia just into northern Tolima; but the material seen from the Magdalena valley is an extreme form of the species with greatly dilated bracts and characteristic bicolored foliage greatly different from sympatric or nearly sympatric S. trianae.