Senna talpana

  • Title

    Senna talpana

  • Authors

    Howard S. Irwin, Rupert C. Barneby

  • Scientific Name

    Senna talpana H.S.Irwin & Barneby

  • Description

    93.  Senna talpana Irwin & Barneby, sp. nov., flore deficiente affinitatis inscrutabilis, sed ex similibus speciebus mexicanis notularum harum coitu extrieanda: foliola ampla penninervia 4-5-juga ±5.5-7 x 2.5-3 cm usque; stylus filiformis ±11 mm; legumen plano-compressum ±8-9 x 0.7 cm, 16-20-spermum.—MEXICO. Jalisco: barranca in steep mountains 11-12 miles s. of Talpa de Allende in headwaters of a w. branch of Rfo Talpa, ±1650 m, 23-25.XI.1960 (fr jun), Rogers McVaugh 21334.—Holotypus, MICH; isotypus, NY.

    Amply leafy shrubs at anthesis ±2 m with terete striate green annotinous branchlets, appearing glabrous but the lf-stalks and axes of inflorescence in- curved-puberulent and the thin-textured subciliolate lfts thinly or remotely strigulose on both faces with straight appressed hairs up to 0.5-0.8 mm, the foliage strongly bicolored, dull dark green above, pallid-glaucescent beneath, the axillary racemes much surpassed by their subtending lf, all lateral to leafy stems.

    Stipules caducous, not seen.

    Lvs 14-26 cm; petiole including discolored, when dry shrunken pulvinus 4-8.5 cm, at middle 1-2 mm diam, rounded dorsally, shallowly openly sulcate ventrally; rachis 7.5-11 cm, the longest interfoliolar segment 25-32 mm; petiolar glands (much eaten) between all but the distal pair of lfts stipitate, in profile 1.3-2.7 mm tall, the slenderly ovoid-ellipsoid acute body ±0.4-0.7 mm diam; pulvinules 2.5-3 mm; lfts 4-5 pairs, moderately accrescent distally, in outline obovate-elliptic obtuse but obscurely apiculate, the distal pair 5.5-7 x 2.5-3 cm, 2.1-2.4 times as long as wide, at base subsymmetrically cuneate, the margin plane, the slender midrib and 7-8 pairs of filiform camptodrome secondary veins prominulous beneath only, tertiary venulation scarcely perceptible.

    Racemes shortly (7-)10-22-fld, the axis together with slender peduncle 6-11 cm; bracts deciduous, not seen; fruiting pedicels 13-19 mm; perianth not seen; ovary puberulent; style filiform, persistent on young pod, ± 11 mm; ovules 16-20.

    Pod variably spreading-ascending, the stipe 1-1.5 mm, the (immature but almost fully formed) body linear piano-compressed ±8-9 x 0.7 cm, bicarinate by the gently undulate sutures, the stiffly papery valves brown glabrescent veinless, slightly raised over each forming seed, the seed-locules 4.5-5 mm long, as wide as the pod’s cavity, the septa between them very narrow or almost 0; seeds not seen ripe, but evidently oriented with broader faces to the valves and bearing an areole on each.—Collection: 1.

    Openings in forest of oaks, Carpinus, Distylium, Magnolia and Podocarpus, ± 1650 m, locally abundant in the barranca of a w. source of Rio de Talpa, mun. Talpa de Allende, far w. Jalisco, Mexico; known only from the type-locality.— Fl. ±X.

    Because sound classification of Senna requires data from perianth, androecium, pod and seed, the affinity of S. talpana, described from a single collection bearing immature pods, cannot be justly evaluated at present. In gross aspect it suggests some form of distantly allopatric S. guatemalensis, but differs in the long filiform style (±11, not 1-2 mm) which implies a substantially larger flower. Senna multifoliolata, a species of mountainous southern Mexico, has a similar pod and seeds, but differs in the more numerous (7-14, not 4-5) pairs of leaflets. Senna koelziana, which occurs in similar cool upland habitat not far distant from Talpa on Sa. del Halo in southeastern Jalisco, has a similarly elongate style but ovules very much more numerous (±64, not 16-20) which prognosticate a pod (unfortunately not yet collected) either longer, plumper, or both. In the event that the pod of S. talpana breaks up, when fully ripe, into one-seeded segments, the species will be compared to S. skinneri; but this is obviously different in the shorter leaves (3-11, not 14-26 cm), solitary petiolar gland, shorter style (4.5-7, not 11 mm) and xeric habitat. All forms of the polymorphic S. pallida have characteristic 2-3-flowered racemes and glands at base of the pedicels, these wanting in S. talpana. No other Mexican or Central American senna bears any close resemblance to it.