Senna crotalarioides (Kunth) 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
Holotypus, labelled ‘n. 4256. Mexico,’ P-HBK!—Chamaefistula crotalarioides (Kunth) G. Don, Gen. Hist. Diehl. Pl. 2: 452. 1832. Earleocassia crotalarioides (Kunth) Britton ex Britton & Rose, N. Amer. Fl. 23(4): 249 ("crotolarioides"). 1930, exclus. syn. ul
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Synonyms
Cassia crotalarioides Kunth, Chamaefistula crotalarioides G.Don, Cassia vogeliana Schltdl., Earleocassia vogeliana (Schltdl.) Britton
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Description
Species Description - Diffuse leafy perennial herbs with lignescent blackish roots and sometimes a shortly branched aerial caudex, the several hornotinous stems procumbent and incurved-ascending, deeply canaliculate distally, at anthesis (1.5-)2-6.5 dm, either simply pilosulous throughout with subappressed and incurved or partly spreading hairs less than 1 mm or both short-pilosulous and the stems, lf-stalks and inflorescence (exceptionally the lfts) in addition charged with fine lustrous horizontal or ascending setae up to 1.5-4 mm, the short vesture of stems antrorse, the density and proportions of longer to shorter hairs highly inconstant, the lfts pubescent on both faces or exceptionally glabrous above, the axillary racemes at first lateral and surpassed by stem, later forming a leafy-bracteate, shortly exserted corymbose panicle. Stipules flexuously ascending, herbaceous, narrowly lance- or linear-attenuate (6-)8-23 x (0.3-)0.4-l mm, 1-nerved proximally, early brown and dry but long persistent. Lvs (3-)4- 10(- 12) cm; petiole including sometimes discolored but little swollen pulvinus mostly 1.5-4(-4.5) cm, of some diminished distal lvs (not further noticed) shorter, at middle 0.5-1.1 mm diam, strongly 3-ribbed dorso-laterally, the ventral sulcus very narrow; rachis 1.5-4.5(-5) cm; glands ascending from between proximal and often next succeeding 1-3 (but only exceptionally the distal) pairs, slenderly stipitate, in prpfile 1.5-5(-5.5) mm, the stipe glabrous or puberulent, the slenderly lance-fusiform or dorsiventrally compressed and liguliform head 0.15-0.45 mm diam; pulvinules 0.7-1.5 mm; lfts (2-)3-5 pairs, subequal or a little accrescent distally, either the distal or the penultimate pair largest, these obliquely oblong-, ovate- or obovate-elliptic, obtuse mucronulate or commonly deltate- apiculate 15-37(-40) x 6-15(-19) mm, (1.8-)2-3 times as long as wide, at base cordate (rounded) on proximal and cuneate on distal side, the margin plane, the upper face of blade veinless, the slender midrib prominulous beneath and giving rise to 2-5(-6) pairs of weakly raised secondary veins, these often visible only below middle of blade, all expiring short of anastomosis. Peduncles mostly 1.5-4.5(-5) cm, some depauperate distal ones shorter; racemes (2-)3-8(-9)-fld, the axis (2-)4- 12(- 15) mm; bracts resembling stipules but shorter, 3-10 x 0.6-1.3 mm, early dry brunnescent, deciduous by or soon after anthesis; mature pedicels (6-)7-14 mm; fl-buds nodding, oblong-obovate obtuse pilose-pilosulous; sepals elliptic or oblong-elliptic obtuse, scarcely or little graduated, the glabrescent inner ones 6-9.5 mm; corolla zygomorphic, the petals yellow glabrous subisomorphic, spatulate or obovate-cuneate (9-) 11-14.5 mm; androecium functionally 7-merous, the 3 staminodes narrowly oblanceolate, the 7 fertile stamens isomorphic except for length, their anthers narrowly lanceolate in outline, gently incurved, just below apex strangulated and thence dilated into a small urn-shaped 1-porose cup, the 2 stamens next the staminodes short, their thecae 1.9-2.8 x 0.5 mm, the 5 abaxial equal or the 3 opposed to sepals larger, the filaments 2.4-3.3 mm, the anthers 3-4.7 x 0.45-0.65 mm, the thecae of all 7 fertile stamens bicolored, castaneous with a yellow stripe along the lateral grooves; ovary either densely white-pilose or glabrous except for a ventral crest of hairs; style glabrous filiform, distally incurved (2.6-)2.8-4.4 x 0.15-0.2 mm, at apex conical, the stigmatic orifice minute terminal; ovules 22-32. Pod ascending or variously declined, sessile, plumply oblong-ellipsoid, straight or slightly incurved (11-) 12- 19(-20) x (4-)5-7(-7.5) mm, laterally compressed but turgid, rounded at base, obliquely cuspidulate at apex, the cross section elliptic, the thin green valves strigose-pilose with stiff appressed or ascending bulbous-based setae up to 1-1.5 mm or sometimes glabrous, becoming brown and papery, differentiated into broad sutural margins and fuscous central band shallowly corrugate over the seeds, dehiscent downward from the beak, the valves only narrowly gaping to emit the seeds; seeds stacked in 2 interdigitating ranks with broad faces of each turned to its neighbor’s, sometimes distorted by crowding but basically compressed-pyriform, when not deformed 2.6-3.1 x 2-2.4 mm, the light brown testa smooth but scarcely lustrous, neither folded nor colliculate, the elliptic areole 0.5-0.8 x 0.3-0.5 mm; x = 28.—Collections: 25.
Distribution and Ecology - Stony hills, plains and waysides, mostly in chaparral and mesquite-grassland, 1100-2100 m, locally plentiful around the w., s. and s.-e. margins of the Mexican Plateau within and near the s. lobe of Chihuahuan Desert, from n. Durango to Guanajuato, Hidalgo, centr. San Luis Potosi and s.-w. Tamaulipas.—Fl. V-XI, the fruits long persistent, often contemporary with young fls.
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Discussion
Among Brachycarpae with short plump pods enclosing two parallel rows of seeds S. crotalarioides and S. demissa are together distinguished by erect or antrorse stem-pubescence. The weak differences between this pair of species are given in our key and mentioned again under S. demissa. We lately maintained (Irwin & Barneby, 1975, l.c.) a taxonomic distinction within S. crotalarioides between a typical short-pilosulous variety and a var. vogeliana both pilosulous and pilose with fine shining white setiform trichomes up to 4 mm long. Accumulated evidence, however, shows that these pubescence forms, which are otherwise identical, have essentially the same range of dispersal. They have been found in close proximity in Durango and San Luis Potosi and in a mixed population near Zimapan, Hidalgo (Irwin 1342). An erratic expression (or suppression) of setose vesture occurs elsewhere in Senna (e.g. S. mutisiana) and is commonplace in Chamaecrista sect. Chamaecrista.
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Distribution
Durango Mexico North America| Guanajuato Mexico North America| Hidalgo Mexico North America| San Luis Potosí Mexico North America| Tamaulipas Mexico North America|