Senna pallida var. brachyrrhachis

  • Title

    Senna pallida var. brachyrrhachis

  • Authors

    Howard S. Irwin, Rupert C. Barneby

  • Scientific Name

    Senna pallida var. brachyrrhachis H.S.Irwin & Barneby

  • Description

    177g(bis). Senna pallida (Vahl) var. brachyrrhachis Irwin & Barneby, var. nov., omnibus cum var. longirostrata conveniens nisi foliis primariis abbre- viatis 3-6.5 (nec 6-13) cm longis, rachi 1-3 tantum (nec 3-9) cm longo, foliolisque plerumque 4-7 (nec 6-9)-jugis, longioribus 9-17 (nec 18-35) mm longis.-MEXICO. Oaxaca, distr. Sola de Vega: en encinar-pinar, 1800 m, 19.X. 1976 (fl), M. Sousa et al. 6297.-Holotypus (2 sheets) MEXU.

    Shrubs or treelets ±2 m tall, sparsely minutely strigulose distally, the lfts ciliolate and their midrib puberulent beneath, otherwise glabrous, the annotinous branchlets pallid, striped lengthwise, the racemes mostly terminal to brachyblasts, forming a narrow leafy thyrse.

    Stipules subulate setiform 2.5-5 x 0.15-0.3 mm.

    Primary lvs 3-6 cm; petioles (1.2-) 1.5-3 cm; rachis 1-2.3 cm, mostly shorter than petiole, the longer interfoliolar segments 2-5.5 mm; leaflets (3-)4-6 pairs, strongly accrescent distally, obovate or oblong-elliptic obtuse or emarginate, the distal pair 9-15 x 4-9 mm, ±2-2.5 times as long as wide, the margins plane, the midrib prominulous beneath, the 4-6 pairs of secondary venules discolored but immersed beneath; gland between proximal pair 2-3 x 0.2-0.5 mm.

    Peduncles 9-19 mm, 2-3-fld; pedicels 10-13 mm; sepals glabrous dorsally, the broad inner ones 7-8 mm; longer petals 15-17 mm; filaments of long stamens pilosulous 4-5 mm, their anther, including tubular beak, 5.5-7 mm; ovules ±38.

    Stipe of pod (not seen fully ripe) ±3 mm, the linear body 6.5-7 x 4 mm, the valves plane.-Collections: 7.

    Pine-oak woodland, 1300-2150 m, locally plentiful in Sa. Madre del Sur in Oaxaca (distr. Sola de Vega) and in the highlands of Chiapas (mun. Tzimol, Totolapa, La Trinitaria, Las Margaritas and Amantenango del Valle).-Fl. VII-I.

    This montane variety is closely akin to var. longirostrata, but differs in the abbreviated leaf-rachis and smaller, more crowded leaflets, the dimensions given in our diagnosis. Representative material of it was seen by us only when our manuscript was, as we thought, finished, but in time to intercalate the description next following the closely related Guatemalan var. longirostrata.