Senna vargasii

  • Title

    Senna vargasii

  • Authors

    Howard S. Irwin, Rupert C. Barneby

  • Scientific Name

    Senna vargasii (Schery) H.S.Irwin & Barneby

  • Description

    123.  Senna vargasii (Schery) Irwin & Barneby, comb. nov. Cassia vargasii Schery, Ann. Mo. Bot. Gard. 37: 401. 1950.—"PERU: CUZCO: Prov. Urubamba, Machupicchu, Feb., 1938, C. Vargas C. 955."—Holotypus, MO! = NY Neg. 10620.

    Doubtless shrubby but of unrecorded stature, the annotinous branchlets, foliage and inflorescence densely pilosulous with rather coarse spreading lutescent hairs ±0.4-0.6 mm, the foliage bicolored, the ample submembranous lfts above dull olivaceous and only thinly pubescent, beneath especially along the veins densely so and pallid, the early racemes axillary to and shorter than lvs, later ones perhaps forming an exserted panicle.

    Stipules reflexed, thinly herbaceous, ovate ±6-7.5 x 3 mm, persistent into full development of associated lf, then apparently deciduous.

    Lvs up to 19 cm, the stout petiole ±2-2.5 x 0.2 cm; rachis 8-10.5 cm, its longer interfoliolar segments ±2-2.5 cm; gland between proximal pair of lfts sessile ovoid-acuminate ±1.5 x 0.8-1 mm, and smaller glands between 2-3 succeeding pairs; lfts 5-6 pairs, strongly accrescent distally, the distal pair subsymmetrically elliptic acuminulate ±6-7 x 2.2 cm, the shorter middle and proximal pairs ovate, the margin of all revolute, the midrib with ±10-12 pairs of camptodrome secondary veins deeply impressed on upper and prominent on lower face, tertiary venulation imperceptible above, obscure beneath.

    Peduncles stout ±7 cm; young racemes shortly densely ±10-15-fld, the expanded fls raised to level of the subglabrous buds, the axis apparently little elongating (but not seen mature); bracts submembranous ovate ±6-6.5 x 2.5-3 mm, persistent at least into full anthesis; pedicels ±26 mm; sepals submembranous brownish obovate or oblong-obovate obtuse, strongly graduated, the outermost ±6 mm, the innermost ±11 mm; corolla zygomorphic, the flabellate-emarginate vexillar petal 15 x 17 mm, the 2 lateral petals almost as long and likewise sub- sessile, the 2 abaxial petals short-clawed and slightly shorter; blade of 3 adaxial staminodes broadly ovate ±2.5- 2 mm; 7 anthers thin-textured brownish glabrous, the 4 median ±5x1 mm, obliquely truncate, the filaments of 2 latero- abaxial stamens ±6 mm, their lunately linear horizontally truncate anther 7.5 x 1.3 mm, the centric abaxial stamen substerile, its anther ±6 x 0.8 mm, the orifice of all 1-porose by confluence; ovary densely appressed-pilosulous; style linear almost straight glabrous ±4.5 x 0.2 mm, its minute stigmatic cavity obliquely terminal; ovules ±35.

    Pod unknown.—Collection: 1.

    Habitat not recorded, but to be sought on rocky hillsides or stream banks of Cordillera de Vilcabamba in Cuzco, Peru, known at present only from the Uru- bamba valley near Machupicchu.—Fl. II-IV(?).

    Senna vargasii is certainly a distinct species, but its affinities will remain unknown until more can be learned about it. The type-collection, consisting of a branchlet at the earliest phase of anthesis, suggests the more pubescent forms of S. burkartiana from Cochabamba, Bolivia, but differs in the reflexed and dilated stipules. Schery thought it related to S. multiglandulosa (Cassia tomentosa) and S. santanderensis, and we agree that its affinities lie probably with this group of ser. Coluteoideae, with which S. vargasii agrees in the relatively low ovule- number, prefiguring a laterally compressed rather than terete pod.