Senna caudata (Standl.) H.S.Irwin & Barneby
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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 1: 1-454.
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Family
Caesalpiniaceae
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Scientific Name
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Type
Typus infra sub. var. caudata indicatur.
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Synonyms
Cassia caudata Standl.
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Description
Species Description - Slender, amply leafy shrubs 1-2 m with terete, remotely minutely livid-verruculose hornotinous branchlets, glabrous up to the minutely puberulent terminal panicle of ±2-5 short racemes of large fls, the thinly chartaceous olivaceous dull or sublustrous lfts concolorous or weakly brunnescent beneath, the inflorescence surpassed by foliage. Stipules (scarcely known) subulate, 2-? mm, caducous. Lvs 3-4.5 dm; petiole including wrinkled (when dry shrivelled) pulvinus 6-12 cm, at middle 1.6-2.5 mm diam, except for prominulous ribs subterete, very shallowly grooved ventrally; glands between lower or both pairs, sessile or almost so, ovoid or oblong or oblong-ovoid obtuse 1.6-3 x 0.7-1.8 mm glabrous; rachis 3.5-6.5 cm, shorter than petiole; distal pair of lfts subsymmetrically ovate or ovate-elliptic, caudately acuminate (acumen ±1.5-3 cm) 15-25 x 5.5-10 cm, ±3-4.5 times as long as wide, at base subequally cuneate or rounded-cuneate on both sides, the margin plane, the almost straight centric midrib above immersed or canaliculate-depressed, beneath cariniform, the ±9-12 pairs of major camptodrome secondary veins and subsequent tertiary venulation finely prominulous on both faces but a trifle more pronounced beneath, the ultimate areoles mostly >0.5 mm diam. Racemes 6-14-fld, the axis including short peduncle 2-4.5 cm; bracts ovate- acuminulate ±1.5 mm deciduous; pedicels 2.5-4 cm; buds globose when young, puberulent, expanded before anthesis of fl; sepals subpetaloid, strongly graduated, ovate-oblong or broadly obovate obtuse, the short outermost one 4-5 mm, the largest inner one 8-9 x 4.5-6 mm, all delicately 4-6-nerved; petals yellow, dorsally puberulent along veins, glabrous within, ± heteromorphic, the adaxial one longest or broadest or both, obovate-flabellate 20-30 mm, the rest obovate to oblong-oblanceolate, either narrower or shorter, one abaxial one involutely cupping 2 long stamens; androecium functionally 7-numerous; filaments remotely or thinly puberulent, of 4 median stamens 1.7-2.7 mm, dilated (especially distally), of 3 abaxial ones 2.5-5 mm, the anthers glabrous, finely papillate, those of 4 median stamens oblong slightly incurved 4-6.5 mm, graduated into 2 sets (the pair more abaxial smaller), with divaricate biporose beak ±0.5 mm, those of 3 abaxial ones deeply lunate-incurved 7-9 mm, with sigmoidally porrect beak 0.8-1 mm, the orifice divided by a slender septum; ovary densely strigulose; style slender, scarcely dilated at tip, 0.5-0.7 mm diam just below stigma, the orifice ±0.3 mm diam; ovules (of var. caudata) ±110. Pod (of var. diadena) described under that variety.
Variety Key - Key to the Varieties of S. caudata 1. Gland between proximal pair of leaflets only; long interior sepals ovate ±4.5 mm wide; petals up to 20-26 mm; e. Panama. 48a. var. caudata (p. 198). 1. Glands between both pairs of lfts; long interior sepals obovate-suborbicular ±6 mm wide; petals up to 26-30 mm; s. Costa Rica (Pacific slope). 48b. var. diadena (p. 198).
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Discussion
A rare species, known to us by only five collections from two restricted areas, one in eastern Panama and the other in southern Costa Rica, the pod and seeds, moreover, from Costa Rica only, a sample inadequate to demonstrate the full range of morphological variation. In consequence the specific status of S. caudata and the taxonomic rank assignable to the two varieties described below must remain provisional. The whole species appears very closely related to and perhaps not distinct from Colombian S. huilana, similar in details of the flower but different in the sharp and intricate reticulation of most leaf-blades, which are, in addition, less abruptly and more shortly caudate or merely bluntly acuminate at apex. Panamanian var. caudata differs further from vicariant S. huilana, which appears to grow at submontane elevations in the northern Andes and not in the wet Pacific lowlands, in the relatively small flower; whereas Costa Rican var. diadena, which may possibly deserve specific status, differs from both of these in a second petiolar gland. The only pod seen, from Puntarenas, Costa Rica, is unlike that of any other member of ser. Bacillares in the narrowly winged valves and thickened spongy septum separating the two files of seeds. In practice S. caudata has been distinguished from sympatric Bacillares by the strongly differentiated sets of stamens, the androecium being almost that of distantly allopatric South American S. georgica.