Senna apiculata (M.Martens & Galeotti) 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. apiculata indicatur.
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Synonyms
Cassia apiculata M.Martens & Galeotti
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Description
Species Description - Slender prostrate or diffusely ascending, precociously flowering perennial herbs from an ultimately woody blackish root, at anthesis 0.6-3 dm, strigulose-pilosulous throughout with shorter incumbent and longer straight appressed or ascending (spreading) hairs to ±0.6-0.8 mm, the short vesture of stems retrorse, the whole vesture of both faces of lfts antrorsely appressed-silky, the lf-blades bicolored, yellowish-green above and gray beneath, the few-fld racemes axillary surpassing their lf, all lateral and not forming a terminal panicle. Stipules ascending, when long flexuously so, linear-attenuate or setiform 3-8 x 0.3-0.6 mm, often charged at base on one side with a small fusiform gland, this however often minute or wanting, the blades becoming dry and mostly deciduous before the lf. Lvs (2.5-)3-13 cm; petiole including firm discolored, hardly swollen pulvinus 13-50 mm, at middle 0.4-0.6 mm diam, narrowly obscurely sulcate ventrally; rachis 10-45 mm, either longer or shorter than petiole; gland (often eaten) between proximal pair only, slenderly stipitate, in profile 0.8-2 mm, the stipe usually puberulent, the lance-fusiform acute orange head 0.1-0.2 mm diam; pulvinules 0.5-1.3 mm; lfts 3-5 pairs, little accrescent distally, obliquely elliptic or obovate- elliptic obtuse mucronulate or deltately apiculate, the largest (10-) 12-40 x 5-14 mm, (2-)2.2-2.5 times as long as wide, at oblique base cordate on proximal and cuneate on distal side, the margin plane, the faces veinless except for the slender midrib prominulous only dorsally, this sometimes giving rise to 1-3 pairs of weak secondary veins visibly raised only on proximal half of 1ft. Peduncles (2-)2.5-10 cm; racemes loosely (l-)2-5(-6)-fld, the axis (0-)2-20(-25) mm; bracts narrowly lanceolate 2-4.5 mm, persistent into or past anthesis, then deciduous; pedicels 5-20 mm; fl-buds nodding, plumply obovoid pilosulous; hypanthium deeply concave, urn-shaped in fruit; sepals elliptic or oblong-elliptic obtuse, the outer greenish, the inner with petaloid dark-venulose margins, all of ± equal length (4.5-)5-11 mm, deciduous with or shortly after petals; corolla zygomorphic, the yellow petals drying yellow or stramineous dark-veined, glabrous or dorsally pubescent near claw, almost isomorphic 11-16 mm, the blades beyond short claw obovate or oblong-obovate obtuse or emarginate; androecium glabrous, functionally 7-merous, the 3 staminodes narrowly oblanceolate, the 7 fertile stamens alike except slightly accrescent toward abaxial side of fl, the filaments 1.6-2.5 mm, the slenderly lance-oblong, gently incurved anthers 1.8-4 x 0.55-0.7 mm, brown striped with yellow in the lateral grooves, at apex bluntly conical and obliquely 1-porose; ovary densely white-pilosulous; style glabrous linear 1.8-2.5 x 0.15-0.2 mm, the minute stigmatic cavity symmetrically terminal; ovules 22-24. Pod widely ascending, perhaps sometimes humistrate, sessile, in profile narrowly oblong-elliptic or -oblanceolate, slightly incurved or almost straight, 2-2.5 x 0.5 cm, obliquely cuspidate at apex, compressed but plumply turgid at maturity, the papery valves in texture and corrugation like those of S. crotalarioides, at once minutely puberulent and strigulose or hispidulous with ascending or subappressed straight setules up to 0.5-0.8 mm; seeds 2-seriate in 2 inter- digitating ranks, oriented as in S. crotalarioides and similar in outline, ±2.8-3.7 x 1.8-2.4 mm, the testa densely intricately rugulose-colliculate overall, the sculpture pale against the almost concealed fuscous background, the areole 0.5-0.7 x 0.3-0.5 mm.
Variety Key - Key to the Varieties of S. apiculata 1. Larger lfts 1-2.7 x 0.5-1.1 cm; peduncles 2.5-8.5 cm; pedicels 5-10 mm; sepals 4.5-6 mm; petals 11-12 mm; s.-e. Puebla. 78a. var. apiculata (p. 275). 1. Larger lfts ±4 x 1.7 cm; peduncles 8-10 cm; pedicels 18-20 mm; sepals 10-11 mm; petals ±15-16 mm: Hidalgo. 78b. var. longipes (p. 275).
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Discussion
This local and seldom collected senna was referred by Bentham to Cassia crotalarioides and has not been extricated from it since. It does indeed resemble some slender forms of S. crotalarioides in general habit but differs in the retrorse short vesture of the stems, in the presence of a gland on the stipules, in the bluntly conic-tipped, not infra-apically strangulated anthers, and particularly in the elaborately sculptured testa of the seeds. In all these characters it agrees rather with S. argentea and S. arida, but differs from both in the filiform style about ten times as long as its apical diameter.