Chamaecrista flexuosa (L.) Greene
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Authors
Howard S. Irwin, Rupert C. Barneby
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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.
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Family
Caesalpiniaceae
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Scientific Name
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Type
Typus infra sub var. flexuosa indicator.
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Synonyms
Cassia flexuosa L.
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Description
Species Description - Precociously flowering but often ultimately suffruticose or rarely truly frutescent herbs variable in habit, stature, and pubescence, with 2—several humifuse, procumbent, assurgent, or erect, always abruptly flexuous and bluntly 4-angular stems at anthesis (1-) 1.5-12, rarely 30 dm, arising from the sometimes dilated crown of the blackish woody root or (in age) from a distinct lignescent caudex, except for the always strigulose ovary nearly (quite) glabrous or variably pubescent with short, forwardly incurved hairs, pilosulous with fine spreading-incurved hairs, or hispid with fine septate setae to 1—2.5 mm, either type of vesture predominant or either 0, the stems and foliage in consequence green or grayish, the small firm crowded, often very numerous, concolorous, dorsally venulose lfts sensitive and in most dried specimens closely imbricated along the lf-stalk. Stipules ± heteromorphic, the lowest small, ovate, not further noticed, the median and upper stiffly ascending, obliquely lance- to dimidiately or subsymmetrically ovate-acuminate, apiculate-mucronate or stiffly aristulate, (3—)3.5—18(—28) x 1 -5—8(— 12) mm, at base broadly semi-cordate-amplexicaul or, when broad, cordate on both sides, the stiffly chartaceous persistent blades coarsely (7-)8-15-nerved from pulvinule, on either or both sides either glabrous or puberulent, the margins smooth, scabrous-ciliolate, or erratically setose. Lvs stiffly widely ascending or slightly recurved, short-petiolate, heteromorphic, the lowest relatively short and simple (not further described), the median and upper most commonly 4—11(—14, in var. texana only 1.5-4.5) cm, the expanded blade varying from narrowly ovate to linear-lanceolate or almost linear- oblong, the lowest and uppermost lfts commonly smallest; petiole (1—)1.5—5.5(—10) mm, openly shallow-sulcate; petiolar glands 1—4(—5), shallowly cup- or saucershaped, circular or rarely elliptic in outline, thick-rimmed, pallid or livid, the largest of them 0.2-0.9(-l) mm diam, sessile or raised on a thick cylindric or distally dilated stipe mostly not over 0.3, rarely to 0.6-0.7 mm, in profile commonly tub- or drum-shaped, rarely tack-shaped; rachis not over 7 mm shorter than lf, rounded dorsally, sharply winged ventrally, the wing emarginate at insertion of each pair of lfts, hence crenate in profile, and also on each side, behind insertion of lfts, again narrowly winged or ridged; lfts (variable both within and between vars.) 9-60(-65) pairs inserted 1—2(—2.5) mm apart along rachis, linear- oblong, -oblanceolate, or narrowly oblong-elliptic, straight or slightly falcate distally, (1—) 1.5—11(—13) x (0.4-)0.5-2.1(-2.5, in Colombia exceptionally 3) mm, at apex abruptly deltate acute or subacute, callous-mucronulate or rarely aristulate, at base on proximal side angulately semi-cordate-auriculate, on distal side narrowly cuneate, from pulvinule coarsely venose by the strongly displaced or submarginal midrib and (on broad side) always by 1 equally strong lateral nerve produced to anastomosis at tip of lft, these both either simple or weakly forked distally, relatively broad lfts also with 1—2(—3) shorter exterior nerves ascending 1/4-1/3 length of the coriaceous or firmly chartaceous blade, the venation always coarsely prominent beneath, fainter above. Peduncles exactly axillary 0-1.5 mm, l-2(-3)-fld; pedicels ascending, straight or incurved under the pod, 11-42 mm, glabrous or puberulent, exceptionally setulose, bracteolate shortly below calyx; bracteoles narrowly ovate or subulate, 1-3-nerved, 0.8-1.7 mm; buds ovoid-acuminate, strigulose or minutely pilosulous; sepals lance-acuminate to ovate acute, the outer often red or red-tinged, the inner hyaline-margined, the longer to 5-13 mm; petals pale or bright yellow, wilting by mid-day and fading during the first day to orange or pinkish-brown, 4 similar, obovate-cuneate or obovate narrowed to a short distinct claw, up to (10.5—) 11.5—18(— 19) mm, the cucullus ± as long but broader, dimidiately or very obliquely ovate, incurved distally, commonly enfolding the gynoecium; stamens 10, the inner series shorter, sometimes infertile, the anthers yellow, the adaxial pair of the larger outer whorl incurved-connivent, the 3 abaxial straight or almost so, to 4.5-8.5(-9) mm; style usually thinly puberulent to middle, linear-cylindric and obscurely clavate toward apex, incurved or hooked distally, 4-9 mm; ovary gray-strigulose; ovules 8-22. Pod ascending, linear-oblong, straight or slightly curved, 2.5-7 x 0.35-0.5 cm, the castaneous or purplish-brown, finally nigrescent valves minutely puberulent; seeds obtusely quadrate, 3-3.9 mm, the testa pinkish- or grayish-ochraceous, dull or scarcely lustrous, sprinkled or lineolate with small shallow fuscous pits, sometimes faintly fuscous-lined along truncate or retuse distal keel.
Variety Key - Key to the Varieties of Ch. flexuosa 1. Major cauline lvs, especially those subtending fls, 4-14 cm, with up to (20-)25-65 pairs of lfts; pedicels always far surpassed by the lf-stalk; pod (3.5-)4-7 cm, 10-22-seeded; s. Mexico and Cuba to n. Argentina. 21a. var. flexuosa (p. 698). 1. Major cauline lvs 1.5-4.5 cm, with 9-20(-25) pairs of lfts; pedicels either longer or only a trifle shorter than the lf-stalk; pod 2.5-4.7 cm, 8-12-seeded; s. Texas to s. Mexico, where confluent with the preceding. 21b. var. texana (p. 700).
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Discussion
Our concept of the weedy and polymorphic Ch. flexuosa is here expanded a little beyond the traditional limits to admit plants differing from what has been considered typical in their relatively short adult leaves composed of fewer pairs of otherwise identically similar leaflets. Such leaves occur in all individuals of the species, but in the races called typical only low on the stems or branchlets, quickly giving way to longer, more elaborately pinnate ones distally. With this modification Ch. flexuosa incorporates without strain the North American Cassia texana and C. itzana which are, however, still maintained collectively as a well- marked variety. As redefined, Ch. flexuosa is distinguished from all other American chamaecristas, except the closely related Ch. parvistipula, by form of the leaf-rachis and venation of the leaflets, further from all those with exactly axillary peduncles and pale seeds by the stiff, abruptly flexuous stems and high number of leaflets, and from Ch. parvistipula and Ch. gonoclada, which see for emphasis, in the form of the root and the closely spaced leaflets. The characteristic rachis of Ch. parvistipula and Ch. flexuosa is rounded on the abaxial side, narrowly winged or ridged laterally, and more emphatically winged ventrally, the wider interfoliolar wing, which corresponds to the herbaceous margins of the ventral sulcus closely appressed or partly fused together, being indented between each pair of pulvinules, in consequence crenulate in profile. Between this and the lateral ridges lie a series of little oblong depressions running parallel with each interfoliolar segment and of the same length. Venation of the leaflet varies with breadth of blade in the number of exterior venules arising from the pulvinule, but is uniform in one striking feature: two equally strong veins arising from the pulvinule and attaining the tip of the leaflet blade, where they anastomose into the mucro, that on the blade’s narrow distal side being the strongly displaced or submarginal midrib, the other the first lateral nerve on the blade’s broader side. This basic venulation pattern serves by itself to distinguish the group of Ch. flexuosa and Ch. parvistipula from all American chamaecristas at all similar in general facies. Key to the Varieties of Ch. flexuosa 1. Major cauline lvs, especially those subtending fls, 4-14 cm, with up to (20-)25-65 pairs of lfts; pedicels always far surpassed by the lf-stalk; pod (3.5-)4-7 cm, 10-22-seeded; s. Mexico and Cuba to n. Argentina. 21a. var. flexuosa (p. 698). 1. Major cauline lvs 1.5-4.5 cm, with 9-20(-25) pairs of lfts; pedicels either longer or only a trifle shorter than the lf-stalk; pod 2.5-4.7 cm, 8-12-seeded; s. Texas to s. Mexico, where confluent with the preceding. 21b. var. texana (p. 700).