Monographs Details: Chamaecrista gonoclada (Benth.) 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 2: 455-918.
Synonyms:Cassia gonoclada Benth.
Description:Species Description - Functionally herbaceous from a xylopodium, the incurved-ascending, simple or weakly branched, strongly nbbed, distally flexuous stems at anthesis 2.5-4.5 dm, appearing glabrous but the young stem, lf-stalks, axes of inflorescence, ovary, and sometimes the lft-margins minutely strigulose with appressed or incumbent hairs up to 0.15-0.4 mm, the foliage concolorous, the lfts when dry dull brownish-olivaceous, conspicuously pallid-veined dorsally. Stipules stiffly ascending, very obliquely ovate-acuminate, those subtending major lvs (5—)7—15 x (2-)2.5-7 mm, at base deeply cordate on the broader amplexicaul side, rounded to cuneate on the other, the firmly chartaceous blades from base strongly 9-14-nerved, glabrous on both faces, only minutely if at all ciliolate. Lvs mostly narrowly ascending, heteromorphic, the lowest and sometimes some distal ones relatively short and simple, the middle and most upper (as described hereafter) 5.5-10 cm, short-petiolate, the expanded blade narrowly lance-oblong-elliptic in outline; petiole with pulvinus 2.5-8 mm, below the gland 0.55-1.2 mm diam, narrowly wing-margined, the sulcus forced open by the gland but beyond this, and throughout the rachis, closed, the rachis-segments thus winged ventrally and also faintly ridged laterally; gland solitary near middle of petiole sessile, suborbicular-patelliform 0.7-1.7(-2) mm diam; lfts (9-) 12-25 pairs inserted on rachis at intervals up to 3-3.5 mm, the firmly chartaceous blades linear-oblong or narrowly oblong-elliptic, symmetrically or obliquely acute mucronulate, up to 9-20 x (1.4-)2-4.4(-5) mm, at base cordate or cordately angulate on the proximal side, cuneate on the distal one, from pulvinus coarsely 4-7(-8)- nerved by the strongly excentric midrib with, on its narrow side, 1 submarginal nerve produced nearly to apex, and on the broad side 1 strong interior nerve anastomosing with the midrib into the terminal mucro together with l-4(-5) exterior ones progressively shorter, these all raised on both faces but more sharply so beneath, the secondary pinnate venulation fainter, not forming a closed mesh. Peduncles exactly axillary 0-1 mm, 1-3-fld; pedicels strictly ascending (1.3—)1.5—4 cm, bracteolate 2-9.5 mm below calyx; bracteoles membranous ovate or lance-acuminate 1-2.8 mm, persistent; buds ovoid-acuminate, minutely strigulose at base only or to middle; sepals brownish, pallidly membranous-margined, lance- or ovate-acuminate 9-12 mm; petals (of Ch. flexuosa) the plane ones up to 12-15.5 x 7-9 mm, the cucullus scarcely or not longer but obliquely dilated; androecium 10-merous, the long anthers up to 6-7.5 mm; ovary strigulose; style 5-7.5 x 0.2-0.5 mm, not dilated at tip; ovules 10-14. Pod (little known) erect, ±45-55 x 5-5.5 mm, the reddish-brown valves minutely sparsely strigulose; seeds unknown.—Collections: 7.

Distribution and Ecology - Campo and cerrado, probably not above 400 m, local, best known from Sa. Maracajú in s.-w Mato Grosso and adjoining Paraguay, from Camapuã to the sources of río Apa (19°30'-22°30'S), collected once in the upper Paraguay valley near Amolar, Mato Grosso (18°S) and once (fugitive from upstream?) on the banks of the lower Paraná (near 27°20'S) in extreme n.-w. Corrientes, Argentina.—Fl. X-V.

Discussion:A precariously characterized species, intermediate between the already very closely related Ch. flexuosa and Ch. parvistipula, having as it were the cordate stipules and decamerous androecium of the former combined with the relatively few, larger and more distant pairs of leaflets of the latter. The leaflets of Ch. gonoclada tend to be a trifle broader and the petiolar glands larger than in its immediate kindred, but no discontinuity has been found in the ranges of variation. It seems reasonable to suppose that Ch. gonoclada arose from the richly variable matrix of Ch. flexuosa and in turn gave rise, with reduction of stipules and androecium, to the yet more specialized Ch. parvistipula, now vicariant in range to the northeastward. The latter and Ch. gonoclada, endemic to the cerrado (or llano) grasslands, are clearly more specialized ecologically than the widespread and adaptable Ch. flexuosa.
Distribution:Mato Grosso Brazil South America| Corrientes Argentina South America| Paraguay South America|