Chamaecrista pilosa (L.) Greene

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.

Family

Caesalpiniaceae

Scientific Name

Chamaecrista pilosa (L.) Greene

Type

Typus infra sub var. pilosa indicator.

Synonyms

Cassia pilosa L.

Description

Species Description - Precociously flowering perennial herbs at length weakly suffrutescent but of short duration, with 3-several simple or distally much-branched stems (1—) 1.5—13 dm procumbently radiating, assurgent, or less often suberect from the crown of a deeply penetrating blackish taproot, the stems, margins of stipules and sometimes of lfts pilose with fine divaricate lustrous septate setae up to (1—) 1.5—4.5(—5) mm and the stems often in addition, either all around or in lines, puberulent with short incurved hairs, these exceptionally extending to the dorsal face of the usually ample, thin-textured ciliolate lfts, the foliage pale green concolorous, the stramineous wiry pedicels smooth and glabrous. Stipules erect, appressed to stem, submembranous, disregarding some small narrower ones at base of stems all obliquely lance- to semi-ovate, -acuminate or -caudate, stiffly mucronulate or weakly aristate, (5—)6—16 mm, at semicordate base 1.5-4 mm wide, palmately 7-13-nerved from pulvinule, the nerves all sharply prominulous beneath, the margins ciliolate and often also ± setose. Lvs (1—) 1.5—4.5(—5) cm, shortly petioled, the larger cauline mostly at least 2 (but on basal shoots regenerating after browsing or late on some vigorous stems only 1-2) cm, all shortly petiolate, the expanded blade commonly ovate (in a rare var. lanceolate) in outline, the lfts of subequal size or commonly shorter and progressively more sharply pitched forward distally, the last pair strictly ascending from tip of rachis and often broadest; petiole 2-6 mm, narrowly margined and shallowly open-sulcate; gland (sometimes 2 in var. luxurians) situated either below or above middle of petiole proper, shallowly cup-shaped, usually thin- rimmed, greenish, livid or reddish, 0.1-0.25 mm diam, elevated on a very slender stipe 0.1-2.7 (commonly 0.1-0.35) mm, in var. pilosa often either deciduous or obsolete; lfts mostly 2-5, in var. luxurians to 11 pairs, oblong-oblanceolate or the distal pair semi-obovate, all obtuse but abruptly apiculate and mucronulate, 7-24 x 2—8(—9.5) mm, at base broadly obtusely auriculate-semi-cordate on proximal, cuneate on distal side, the moderately excentric penninerved midrib with, on broad side of blade, 2-4(-5) incurved ascending primary veins all sharply prominulous on dorsal, finely so on ventral face. Peduncles subobsolete to 2.5 mm, exactly axillary or adnate to stem through 0.5-1.5(-2.5) mm, commonly 1-2-, rarely 3-6-fld; pedicels ascending, straight or almost so, at anthesis filiform, in fruit wiry stramineous (2-)2.5-5 cm, the longest at any one node usually as long as or surpassing the lf, bracteolate far above middle; bracteoles membranous lance-subulate 1-3-nerved 0.9-3.3 mm; buds slenderly ovoid-acuminate, at least thinly setose; sepals membranous, greenish- yellow or reddish, ovate- or narrowly lance-acuminate, 3.4-5.7(-7) mm; petals yellow, early fading and discolored (pinkish-orange), 4 obovate-cuneate to oblong or elliptic-oblanceolate, ± unequal (2 commonly shorter), the longest up to 3.5-6.5 (-7) mm and either a little longer or shorter than the sepals, 1 lateral one folded to enclose the divaricate gynoecium and one large anther, the cucullus scarcely differentiated, obliquely obovate (4-)4.5-7 mm; stamens of outer whorl perfect, their lanceolate yellow or reddish anthers up to 3.2-4.5 mm, the inner whorl represented by 2—3 adaxial, greatly reduced or rudimentary members, sometimes obsolete; ovary densely gray-strigulose; style cylindric, stoutish, incurved, (1-) 1.3-2.2 mm; ovules (6-)8-17. Pod linear in outline, straight or commonly a little decurved, (1.7-)2.3- 4.7 x 0.3-0.4 cm, the pale green valves becoming stramineous and finally nigrescent, finely incurved-pilosulous, never setose, the persistent style-base short stout, apically dilated, a trifle declined; seeds quadrately oblong-pyriform, 2-2.7(-3) mm, the testa pale ochraceous or brownish with fuscous transverse line at truncate distal end, dull rugulose, faintly pitted, mucilaginous when wetted.

Variety Key - Key to the Varieties of Ch. pilosa 1. Lfts 2-5 pairs, often relatively large, the longest of the major lvs mostly 12+ mm, the expanded lf-blade ovate in outline; petiolar gland either obsolete or minute, elevated on stipe 0.1-0.35(-0.5) mm; widespread circum-Caribbean, to lower Orinoco valley in Venezuela, the Pacific slope in central America, and introduced in Florida. 28a. var. pilosa (p. 719). 1. Lfts (5-)6-11 pairs, relatively short, 7-12 mm, the expanded blade in consequence lanceolate in outline; petiolar gland (often 2) long-stipitate, the stipe 0.8-2.7 mm; n.-e. Brazil. 28b. var. luxurians (p. 720).

Discussion

A chamaecrista of weedy aspect and often weedy habits, notable for the small size of the long-pedicellate flower relative to the usually ample, thin-textured foliage, for the lustrously hispid stems, and a flower which superficially resembles that of the partly sympatric Ch. serpens var. serpens but is in reality different in the always incomplete, if partly present wholly staminodal inner whorl of stamens, the scarcely differentiated cucullus, and the usually shorter style. The var. serpens differs further in its lanceolate, not semi-cordate stipules, and very commonly but not quite reliably in shorter (mostly under not over 1.5 mm) setiform vesture of the stems, on the average smaller and slightly more numerous (5-8, not 3-5) pairs of leaflets, and shorter, commonly 5-9- not 8-17-seeded pod clothed in part with long weak setae, not simply pilosulous. However, starveling individual plants of Ch. pilosa, and some maimed ones regenerating after cutting, resemble var. serpens in the small size (but not number) of leaflets and short, few- seeded pod; these retain the floral morphology intact and usually some distinctly semicordate stipules. A particular, possibly intermediate form from Venezuela is mentioned further under var. serpens. The relationship of Ch. pilosa to the largely allopatric Ch. trichopoda, always easily distinguished from var. pilosa by the many (mostly 11-22) pairs of leaflets, is discussed under Ch. pilosa var. luxurians below. In its extensive but interrupted range north of the Equator Ch. pilosa is, disregarding the minor variation already mentioned, essentially monomorphic and easily distinguished. Remotely distant in southeastern Brazil the species is represented by a variety instantly recognized by leaflet number and great development of the petiolar gland. Key to the Varieties of Ch. pilosa 1. Lfts 2-5 pairs, often relatively large, the longest of the major lvs mostly 12+ mm, the expanded lf-blade ovate in outline; petiolar gland either obsolete or minute, elevated on stipe 0.1-0.35(-0.5) mm; widespread circum-Caribbean, to lower Orinoco valley in Venezuela, the Pacific slope in central America, and introduced in Florida. 28a. var. pilosa (p. 719). 1. Lfts (5-)6-11 pairs, relatively short, 7-12 mm, the expanded blade in consequence lanceolate in outline; petiolar gland (often 2) long-stipitate, the stipe 0.8-2.7 mm; n.-e. Brazil. 28b. var. luxurians (p. 720).