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

Type

Holotypus, F! = F Neg. 53096; of 2 paratypi cited, Macbride & Featherstone 2526 is conspecific, but Weberbauer 7608 = var. huancavensis.

Synonyms

Cassia helveola J.F.Macbr.

Description

Variety Description - Shrubs 1.5-3 m, the young branchlets, lf-stalks and inflorescence densely pilosulous or loosely strigulose with sordid or lutescent hairs to 0.2-0.45(-0.6) mm, even the fl-buds silky-pilosulous and the young pod puberulent; stipules 4-6.5 x 0.8-1.5 mm, densely pubescent dorsally; lvs (5-)6-13 cm; lfts (9-) 10- 14(- 16) pairs, ovate-oblong to narrowly oblong-elliptic, the longest 13-26 x 5-8 mm, (1.9-)2-3.6 times as long as wide, glabrous ventrally, densely pilosulous dorsally, the venation as in var. birostris; racemes (7-)9-35-fld, corymbiform at anthesis; sepals pilosulous dorsally except toward margins, strongly graduated, the outer 3.5-5 mm, the inner 7.5-10.5 mm; petals 11.5-16 mm; filaments of 2 long abaxial stamens 5-8 mm, the anthers as in var. birostris; ovary densely pilosulous; style 1.8-2.3 mm; stipe of (little known) pod ±5-7 mm, the broadly linear body ±9x1 cm.—Collections: 12. [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 densely pilosulous dorsally, the inner ones relatively large, the longest 7-10.5 mm; Pasco, Huanuco, Ancash and La Libertad."]

Distribution and Ecology - Rocky and brushy hillsides, river banks and gravels, sometimes on roadside cuttings, 2300-3250 m, locally plentiful in the Andes of n.-centr. Peru, from the sources of Rio Huallaga in Pasco and Huanuco n.-e., high on Pacific slope, through Ancash into La Libertad (Otusco).—Fl. I-IV.

Discussion

Comments on the close relationship within its species and on differential characters of var. helveola will be found under the vicariant vars. arequipensis and birostris. Care must be taken to distinguish it from sympatric and superficially similar S. versicolor, different at anthesis in having leaflets paler or brighter green above than beneath (contrary to the rule in Senna), in the broader (mostly 1.5-6, not 0.8-1.5 mm), more persistent stipules and in the slightly longer (11.5-16, not 10.5 mm) petals; and instantly separable when ripe fruit is present by the areolate seed-faces.

Distribution

Pasco Peru South America| Huánuco Peru South America| La Libertad Peru South America|