Senna rugosa (G.Don) 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 not located (not at BM!); presumed isotypi, F (fragm ex †B), G, W (Sello 1818/IV)!
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Synonyms
Cassia rugosa Don
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Description
Species Description - Erect or ascending, 1-few-stemmed shrubs or subshrubs from a xylopodium, at anthesis mostly 5- 16(-20) dm, exceptionally subarborescent to 25 dm, pilosulous throughout or almost so with straight spreading or (wholly or partly) incurved, pallid or in the inflorescence often yellowish hairs up to (0.3-)0.35-0.7(-0.8) mm, the branchlets subterete or faintly ribbed, the firm lfts bicolored, sublus- trously green or brownish-green above, paler beneath, usually pubescent on both faces but more thinly so above, occasionally glabrescent above or on both faces, ciliolate, the inflorescence racemose-paniculate, exserted. Stipules erect, narrowly subulate or linear-setiform, (2-)3-9(- 12) mm, at folded base 0.25-0.6 mm wide, caducous. Lvs below inflorescence (4-)6- 13(- 14) cm, short-petiolate or subsessile; petiole including slightly dilated firm pulvinus (1.5-)2.5-12(-20) mm; rachis (10-)12-26(-30) mm, rounded dorsally, depressed-flattened ventrally; glands between each pair of lfts, mostly sessile, ovoid or plumply ovoid-ellipsoid 0.8-2.2 mm tall, the slightly smaller distal one sometimes stipitate and then ellipsoid- fusiform, the proximal one often dorsoventrally compressed and plumply linguiform, both usually hispidulous, rarely glabrate; distal pair of lfts beyond the semi-cordate base subsymmetrically elliptic to elliptic-oblanceolate or obliquely ovate-obovate, obtuse or emarginate (exceptionally deltate) at apex, of larger lvs (4-)4.5-10(-10.5) x (1.5-)1.8-4(-4.5) cm, ±1.6-3 times longer than wide, the margins ± revolute, the straight or slightly incurved midrib giving rise on each side to 6-11(- 12) major secondary venules, these above pallid and finely prominulous, beneath sharply elevated and giving rise to a prominent reticulum of venules enclosing sunken areoles up to ±0.5-1.5 mm diam; proximal pair shorter and often proportionately broader. Peduncles mostly from axils of greatly reduced or obsolete lvs, together with raceme-axis 3-9 cm; racemes shortly and loosely 2-12-fld; bracts submembranous ovate-elliptic, obtuse or acute, cymbiform, 2-4 mm, caducous; pedicels at full anthesis and in fruit (2-)2.5-4.5 cm; sepals submembranous yellowish, at full anthesis widely spreading or deflexed, silky-pilosulous dorsally, the longest oblong to obovate obtuse 6.5-10 x 3-6(-6.5) mm; petals bright yellow, dorsally pubescent (exceptionally glabrous), (17-)20-31(-33) mm, the claw 2-4 mm, that of the slightly wider adaxial petal slightly longer than the rest, the blades obovate- suborbicular to oblong-obovate emarginate, 5-nerved from claw; filaments pilosulous (exceptionally glabrous), of 3 long stamens (2.7-)3-8 mm, of 4 short perfect ones 1.5-3.5 mm; thecae of 3 long stamens 7-11.5 mm with porrect beak 1-1.7(-2) mm, of 4 short ones 4.7-8 mm with abruptly divaricate beak 0.4-0.8 mm, the apical pores of all confluent into a U-shaped slit; staminodes to 3 mm; ovary densely pilosulous, the gently incurved glabrescent style 2.5-5 mm, incrassate and 0.55-0.9 mm diam distally, the stigmatic orifice 0.3-0.55(-0.6) mm diam; ovules (48-)54-94(-102). Pod pendulous, stoutly short-stipitate, the stipe 4-7 mm, the plumply cylindric, straight or slightly incurved body 4-11(-12) x 1.2-2 cm, abruptly obtuse at both ends, the valves at first green turning lustrous black, the immersed sutures brown, the cavity pulpy, the pulp nigrescent; seeds biseriate, turned broadside to the septa, compressed-pyriform but either rounded or depressed at distal pole, 7-8 x 4.5-6 mm, the brilliantly lustrous testa castaneous or mahogany brown, the faintly differentiated areole obovate-oblanceolate in outline, 5-6 x 2.5-3.5 mm.—Collections: 210.—Fig. 11 (androecium), 12 (pod, seed).
Distribution and Ecology - Cerrado, commonly on red clay or gravelly soils, locally on limestone or quartzite outcrops, or (in Para) in campina, mostly between 500 and 1200 m but in e.-centr. Goias ascending to 1300, in s.-centr. Minas Gerais to 1500 m and descending in Bolivia to 370, in s.-w. Para to 420, and in n. Goias to 300 m, widespread and locally abundant, often as an element of regenerating scrub-woodland and as a roadside colonist, over much of the Brazilian Planalto, from Sa. do Cachimbo in s.-w. Para and headwaters of Rio Xingu in n.-centr. Mato Grosso w. and s.-w. to the upper Rio Guapore in s.-e. Rondonia and Sta. Cruz, Bolivia and to Sa. de Amambay along the Brazil-Paraguay border, e. across Goias to w. and centr. Bahia (Espigao Mestre and Chapada Diamantina), centr. Ma- ranhao, s. Ceara, w. Pernambuco and s. Piaui, in Goias n. to near 7°20' in Sa. das Cordilheiras (s. of Araguama), across Minas Gerais to the crest of Sa. do Espinhaço and locally to its e. slope on upper Rio Jequetinonha and Rio Pardo, there entering s.-e. Bahia; s. from Minas, becoming less frequent, through e. centr. Sao Paulo to the sources of Rios Ivai and Paranapanema in n. and n.-e. Parana.—Fl. X-VI(-VIII), most prolifically I-V; fr. mostly (IV-)V-IX.
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Discussion
Among Bacillares as a whole and especially among the large-flowered group with two strongly dimorphic sets of anthers, S. rugosa is a pygmy, either functionally herbaceous from a xylopodium or weakly suffruticose, and at maturity seldom above 1.5 and often less than one meter tall. It is closely related to the emphatically fruticose or arborescent S. macranthera, of which it has essentially the flower; but may always be recognized with ease by the abbreviated true petiole, which is shorter than the stalk between the two pairs of leaflets, by the presence of a gland between the distal pair of pulvinules, and by the alveolately reticulate dorsal surface of the leaflets. The short, plumply sausage-shaped, internally pulpy pod, from which the seeds are tardily released by weathering, is almost that of the much smaller-flowered group related to S. chrysocarpa. The species is one of the two or three commonest true sennas of the Brazilian cerrado and characteristic of it, extending only weakly northward into floristically related savanna and deciduous scrub-woodland communities.
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Distribution
Pará Brazil South America| Goiás Brazil South America| Minas Gerais Brazil South America| Mato Grosso Brazil South America| Rondônia Brazil South America| Santa Cruz Bolivia South America| Bahia Brazil South America| Maranhão Brazil South America| Ceará Brazil South America| Pernambuco Brazil South America| Piauí Brazil South America| São Paulo Brazil South America| Paraná Brazil South America|