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

Authors

Howard S. Irwin, Rupert C. Barneby

Authority

Irwin, Howard S. & Barneby, Rupert C. 1982. The American Cassiinae. A synoptical revision of Leguminosae tribe Cassieae subtrib Cassiinae in the New World. Mem. New York Bot. Gard. 35, part 1: 1-454.

Family

Caesalpiniaceae

Scientific Name

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

Type

Holotypus, collected near La Mejorada, prov. Tayacaja, 21.III.26 (fl jun), F! = F Neg. 53097; isotypus, K!

Synonyms

Cassia helveola var. huancavensis J.F.Macbr.

Description

Variety Description - 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. [Key: "Anthers of 3 abaxial stamens all fertile, of ± equal length (4-7.8 mm) and girth even though the centric one is raised on a shorter filament than its neighbors; style 1.2-2.7(-3.4) mm. Lfts glabrous on upper, often nearly so on lower face, the margins and the midrib on dorsal face ciliolate; widespread along the Andes from Ecuador to Argentina. Plants of Peru s.-ward from 7°S, Bolivia and Argentina; filaments of longer abaxial stamens 3-11 mm; pod (0.75-)0.8-1.3(-1.5) cm wide. Range extending from n.-w. Bolivia through the Peruvian Andean plateau to An- cash and along its Pacific slope from Arequipa to La Libertad; lfts thin-textured if glabrous, often pubescent dorsally; stipe of pod 4.5-8.5 mm. Sepals either pubescent dorsally or some of them smaller, in either case well graduated; e. slope of Andes at ±2200-3500 m between n.-w. Bolivia and La Libertad, Peru, there and in Ancash passing the crest to the Pacific slope. Sepals glabrous or thinly pilosulous dorsally, shorter, the longest inner one 4.5-6.5 mm; Huancavelica and Cuzco, Peru and n.-w. Bolivia."]

Distribution and Ecology - 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.

Discussion

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."

Distribution

Huancavelica Peru South America| Cusco Peru South America| La Paz Bolivia South America|