Monographs Details: Senna hirsuta var. streptocarpa 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.
Description:Variety Description - Except for glabrescent pod softly pubescent throughout with procumbent or ascending and antrorsely incurved hairs up to 0.25-0.7 mm (occasional random ciliae longer), the lfts at least when young densely gray-pilosulous beneath, finely puberulent above; petioles 12-35 mm; rachis (4-)4.5-9 cm; gland globose or squatly ovoid 1-1.7 mm diam; lfts (4-)5-6(-7) pairs, the distal pair ovate- or broadly lance-acuminate 4.5-8 x 1.6-2.8 cm, 2.5-3.4 times as long as wide; peduncles 6-30 mm; racemes (except for some depauperate early and late ones) 8-35(-43)-fld, the axis including peduncle becoming (1.5-)2.5-8(-10) cm; longer sepals 5-7 mm; longer petals 8-13.5 mm; ovules 50-68; pod 10.5-16 x 0.4-0.55 mm, strongly arched outward and spirally twisted through 1-2 turns.—Collections: 16. [Key: "Lfts pubescent on both faces and cili(ol)ate, the longer hairs 0.4-2.8 mm. Vesture of lfts strigulose or softly pilosulous, the hairs when loose commonly incumbent or incurved, less often straight and spreading, in any case not highly lustrous nor more than 0.4-0.7 mm long; S. America in lat. 17-30°S. Pod both arched outward and spirally twisted, commonly sigmoid when flattened in press; racemes mostly 8-35-fld; fls small, the longer inner sepals 5-7 mm, the longest petal 8-13.5 mm; n.-e. Argentina (Misiones) and adjoining Brazil (Rio Grande do Sul)."]

Distribution and Ecology - Campo thickets, matorral, fallow fields, sometimes colonial along roads or in pastures ±70-350 m, locally plentiful in extreme n.-e. Argentina (Misiones) and adjoining Brazil (n. and centr. Rio Grande do Sul), there extending e. into the middle Jacuf valley.—Fl. XI-III(-IV).

Discussion:In his account of Cassia in Argentina, Burkart (1952, l.c.) carefully distinguished two hairy, narrow-fruited sennas of sect. Oncolobium, one entering the northwest of the country from Bolivia and Paraguay, the other weedy in Misiones and adjoining Brazil. The plant of the Chaco and of the Andean foothills in Salta and Tucuman, equivalent to our S. hirsuta var. puberula, was referred by Burkart to C. hirsuta sens. lat. whereas that of the middle Parana-Uruguai valleys, evidently the same as our var. streptocarpa, was misidentified as C. leptocarpa, although very different in detail from the glabrescent plant from Rio de Janeiro to which the name properly belongs. The var. streptocarpa has long been known in herbaria and variously referred either to C. neglecta, from which it differs in the ovate-acuminate rather than oblong-elliptic leaflets and the much narrower pod (4-5.5, not 7.5-14 mm wide) or, following Burkart, to C. leptocarpa, or to C. pubescens Jacqu., which we interpret as synonymous with S. hirsuta var. puberula described immediately following. The dense but soft pubescence of the foliage, the well-furnished racemes of small flowers, and the long narrow glabrescent pod that tends to fall into a sigmoid figure when pressed are the features by which var. streptocarpa may be recognized. The figure of Cassia leptocarpa given by Dimitri & Rial Alberti (1954, p. 25) may well be this.
Distribution:Misiones Argentina South America| Rio Grande do Sul Brazil South America|