Senna birostris var. huancavensis

  • Title

    Senna birostris var. huancavensis

  • Authors

    Howard S. Irwin, Rupert C. Barneby

  • Scientific Name

    Senna birostris var. huancavensis (J.F.Macbr.) H.S.Irwin & Barneby

  • Description

    110c. Senna birostris (Vogel) var. huancavensis (Macbride) Irwin & Barneby, comb. nov. Cassia helveola var. huancavensis Macbride, Field Mus. Bot. 13, part 3(1): 167. 1943.—"PERU. Huancavelica: Montaro Valley, Weberbauer 7608 ..." Holotypus, collected near La Mejorada, prov. Tayacaja, 21.III.26 (fl jun), F! = F Neg. 53097; isotypus, K!

    Senna birostris "var. controversa" Irwin & Barneby, in sched., nom. nud.

    Morphologically and geographically intermediate between var. totorae and var. helveola, resembling the former in habit (but sometimes arborescent to 6 m) and in pubescence, and the latter in the androecium; lfts 8-12 pairs, ciliate on margins and midrib beneath, otherwise glabrous, the longer ones 13-21 x 5-8 mm, all veinless on upper face, delicately penniveined beneath, the 5-7 pairs of camptodrome secondary veins immersed discolored; sepals well graduated, glabrous or almost so dorsally, the outer ones 2.5-4.3 mm, the inner 4.5-6.5 mm; petals up to 7-12.5 mm; filaments of 2 latero-abaxial stamens 3-6 mm, of the centric abaxial one 2.5-4.5 mm, the anthers of 2 latero-abaxial stamens 4-5.5 mm, of the centric one 3.5-4.8 mm; style 1.4-2.2 mm; ovules 20-28; stipe of pod ±5 mm, the linear body 11.5 x 0.9 cm, the seed locules 3.5—4 mm long.—Collections: 5.

    Thickets in the monte formation, 2650-3500 m, on the sources of rfos Montaro, Urubamba, Madre de Dios and Beni in s.-e. Peru (Huancavelica, Cuzco) and adjoining Bolivia (La Paz).—Fl. III-IV.

    The var. huancavensis occupies the geographic gap between var. totorae to the south and var. helveola to the northwest, differing from the former in the presence of a seventh functional stamen, a longer style, and a much longer pod; and from the latter in the shorter, externally glabrous or glabrescent calyx. The first collection of the variety, the widely distributed Mandon 751 which contains distracting fruiting fragments of the only superficially similar S. aymara, was cited by Bentham (1871, p. 540) as Cassia versicolor and has corrupted subsequent accounts of that species. During our preliminary studies of Senna we interpreted this Bolivian plant as undescribed, and unfortunately have annotated a number of sheets in various herbaria as "var. controversa."