Monocarpic but highly variable in stature and vigor, at anthesis (0.4-)l-9(-12) dm, the stem either simple and erect, or branched from near or only well above base (the secondary axes then incurved-ascending), or less often diffuse or humifuse, the most robust forms basally lignescent in age, the whole highly variable in pubescence, the stems and lf-stalks usually both puberulent with short incurved-subappressed hairs and pilose with spreading, pallid or yellowish setae up to 1—2(—2.3) mm, but either type of hair sometimes lacking, the lfts commonly glabrous on both faces, sometimes puberulent beneath, their margins usually either minutely scabrous-ciliolate to ciliate with random longer setae, or rarely smooth, the pod nearly always loosely pilose, exceptionally incurved-puberulent.

Adult lvs (1.5-)2.5-9.5(-ll) cm; petiole 2-5(-6) mm; petiolar glands 1-2, orbicular, cupulate or almost discoid, (0.3-)0.4-l(-l.l) mm diam, stipitate, the stipe either slenderly linear or dilated upward, the whole 0.5-1.7 mm tall, varying in profile from slenderly trumpet-shaped or pileiform to tack-shaped, rarely broadly subuliform, and at least as tall, usually taller than diameter of head; lfts of larger lvs up to (9-)12-25(-28) pairs, linear or narrowly oblong, straight or slightly falcate, up to 6-21 x (1—) 1.3—3 mm.

Pedicels at anthesis (0.5—)1—3.5, in fruit 2-6 mm; longer sepals 3.5-6.8(-8) mm; petals strongly asymmetric, 2(-3) adaxial much shorter than the rest, the longer (l-)2 and the cucullus (2.8-)3.5-6.7(-7, exceptionally -8) mm; stamens (4—)5—10, the longer anthers 1.7-4.5(-4.8) mm; ovary densely subappressed-pilose or barbate; style 0.8-1.6(-2) mm, dilated upward and hooked, at apex (0.3-)0.35-0.7 mm diam; ovules (7—)8— 15(— 16).

Pod (20-)24-52 x 2.5-4.6(-5) mm, the valves usually reddish or castaneous, sometimes green with red sutures, finally nigrescent, loosely pilose or less often merely puberulent; seeds 2.5—3.3(—3.5) mm, the testa fuscous or brownish-nigrescent, not or scarcely lustrous, lineolate, the pits often darker-colored than the ground.—Collections: 174.—Fig. 36 (petiolar nectary).

Open sandy and gravelly hills, savannas, glades in light or disturbed woodland, shores and beaches, becoming a weed along highways, paths and in gardens or orchards mostly below 700 but in Guatemala up to 1200, in s. Mexico up to 1740, in Ecuador up to 2200, in n.-w. Argentina reportedly up to 3000 m, widespread and common in Central America from the Isthmus of Tehuantepec in Mexico to the lower Magdalena valley in Colombia, extending n. in Mexico into the Balsas Depression and (gradually passing into var. mensalis) to the Lerma-Santiago valley in Jalisco and (somewhat disjunct) to the Pacific coast and foothills of s. Sinaloa, also n.-e. around the Caribbean slope to s. Tamaulipas, the Yucatan peninsula, and feebly represented on w. Cuba (Pinar del Río; La Habana) and Jamaica; s. highlands (Loja) and Pacific lowlands (Guayas) of Ecuador; lowland n.-w. Peru (Piura and Tumbes); highly disjunct in n.-w. Argentina (Salta and Jujuy), where perhaps introduced.—Fl. in Mexico and Centr. America VIII-II, in Argentina XII-III, but intermittently through the year if moisture permits, and capable of abrupt regeneration following unseasonable storms.

Our concept of var. jaliscensis encompasses a horde of growth- and pubescence-forms in which a small, highly asymmetric flower with apically thickened style coincides with evidently but variably stipitate petiolar glands as tall or taller than the diameter of the head. Its diverse elements differ collectively from partly sympatric varieties of subsp. patellaria in gland-type, from the latter’s var. ramosa further in the less asymmetric midrib of the leaflets but not in the flower, and from its var. glabrata further in the asymmetric flower but not in the leaflets. From its closer kin within ssp. nicititans it is finally distinguished only by the dilated style, and from subsp. disadena var. pilosa, which has the same style, by the strongly asymmetric corolla and (often) reduced androecium.

The more immediately notable minor variants of var. jaliscensis are those in which the ordinarily abundant long setae of stem, leaf-stalk and stipule-margin are few, small, or wanting, and those which, due probably to edaphic accident, fail to develop a strong erect primary axis and in consequence assume a diffuse or trailing habit. The flower, always very small relative to the foliage, varies considerably in length and amplitude, but this is imperfectly correlated with vigor of growth. Number of stamens is clearly linked to amplitude of the perianth, a 9-10- merous androecium being found commonly in the larger flower that predominates on the Caribbean slope in Mexico and southward, dwindling in Mexico northwestward from Chiapas (except locally in Sinaloa) into a 5-7-merous one. At the same time the style-tip, emphatically dilated southward from Guerrero, fades by insensible steps northwestward into the linear style of var. mensalis, ultimately distinguished by this feature alone. The girth of the pod varies from quite as slender as that of var. mensalis, which is commonly 2.5-3.5 mm, up to 4.5 or even 5 mm in the robust forms which correspond to Britton’s misconception of Cassia stenocarpa Vog. The named segregates which we refer to var. jaliscensis are characterized by particular syndromes of the variable features:

i. Cassia rip aria: Described from an ageing plant in fruit only, but apparently representing the form of var. jaliscensis common in lower Magdalena valley; pod hirsutulous.

ii. Cassia broughtonii: Robust and erect, puberulent but scarcely setose below the pod. This was equated even by Britton with the widespread plant of the Central American states which he called Ch. stenocarpa.

iii. Chamaecrista wilsonii: As the last, but the pod incurved-puberulent, not pilose. 

iv. Chamaecrista longicoma: Pubescent as C. broughtonii but peculiar in var. jaliscensis for the relatively large flower, the long petals up to ±8 mm A closely similar plant with slightly taller glands (Montes & Salazar 507 US) also from Sinaloa, was referred by Britton to Ch. stenocarpa. Both have the long-barbate ovary common in Panamanian var. jaliscensis, 9 or 10 stamens and the dilated style characteristic of their kind, in these characters differing widely from sympatric var. mensalis of the Sinaloan foothills. Fruiting specimens (Mexia 380, CAS) from the same region have pilose pods ±5 mm wide and probably represent the same localized large-flowered race.

v. Chamaecrista nicoyana: Slender, procumbent, short-leaved, either densely or sparsely setose below the pilose pod. The type, from "sommets gazonnes" suggests an ecotype from extremely poor stony soil, comparable to plants flowering at a stature of 5 cm which were collected in river sand in El Salvador (Standley 21192, US). Elsewhere the prostrate or diffuse-incurved growth-habit is associated either with small leaves and flowers (Breedlove & Raven 13244 from Chiapas; Purpus 7850 from Veracruz), or with relatively large leaves and flowers, this in Honduras either inland (Molina 24654, NY) or on the ocean beach (Schipp 720, GH, NY).