Senna pilifera (Vogel) 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. pilifera indicatur.
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Synonyms
Cassia pilifera Vogel
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Description
Species Description - Herbaceous or softly suffrutescent in age, variable in habit and stature, sometimes flowering precociously and appearing monocarpic, at anthesis 1.5-24 dm, variably pubescent with usually 3 sorts of hair: a) minute thickened livid trichomes, b) short soft subappressed, incurved-ascending or spreading villi <1 mm, and c) erect lustrous setae up to 2-4.5 mm, the 3 sorts variably dense and variably proportioned, either of the first 2 sometimes lacking and setae either present on all axes or confined to stipules (exceptionally 0), the foliage ± bicolored, the ample lfts dull green above, paler or glaucescent beneath, either softly pilosulous on both faces, or beneath only, or glabrous, the umbellately (1-)2-3- fld racemes pedunculate in lf-axils, ascending toward the meridian, immersed in foliage or shortly exserted. Stipules erect or subfalcately ascending, narrowly linear-attenuate or setiform (3-)4-14(-15) x 0.2-0.8 mm, firm green, prominently 1-nerved, deciduous with or before the lf. Lvs 3-12(-15) cm, 4-foliolate; petiole including the (when dry) wrinkled pulvinus (0.8-)l-6 cm, at middle 0.5-1.5(-l.7) mm diam, narrowly obtusely thick- margined and openly sulcate ventrally; rachis (2-)3-16 mm; glands ascending from between each pair (the distal rarely lacking), stipitate, the slender stipe either glabrous or puberulent, the whole in profile 1.5-4(-4.5) mm tall, the slenderly ovoid or lance-fusiform acute head either longer or shorter than stipe, 0.2-0.5(-0.6) mm diam; lfts 2 pairs, heteromorphic, the distal pair longer and often proportionately narrower, these varying (sometimes on one stem) from broadly obliquely obovate and obtuse to obliquely rhombic-elliptic and obtuse, deltately acute or rarely emarginate, or (less commonly) lance-ovate-elliptic and acute, 2-6.5(-8) x 1-3.5 cm, 1.3-3(-3.3) times as long as wide, the straight or obscurely incurved midrib with (5-)6-9(-11) pairs of camptodrome and (rarely) a few random intercalary secondary nerves prominulous on both faces, or only beneath, where tertiary and reticular venulation either elevated or not. Peduncles (0.7-)1-9(-11) cm, pseudo-umbellately (l-)2-3-fld, the axis not over 1 mm; bracts 2-3 firm lanceolate, ovate or subulate 1.5-4 mm, tardily deciduous; pedicels (1.3-) 1.5-5 cm; young fl-buds oblong-obovoid obtuse, either glabrous, thinly pilosulous or setose-hispid, separated by the emergent petals long before true anthesis; sepals herbaceous, green with paler margins, commonly heteromorphic but not strongly graduated, the larger inner ones ovate, obovate, elliptic- or lance-oblong obtuse 4.5-13.5 mm, faintly or prominently 5-8-nerved from base; petals yellow, puberulent dorsally, beyond the claw obovate, oblong-obovate or broadly oblance-elliptic, all obtuse or the vexillary one commonly broader and emarginate, of subequal length or the 2 more oblique abaxial ones either a little longer or shorter than the adaxial, the longest petal (12-) 13-36 mm; androecium glabrous, functionally 7-merous, the filaments of 4 median stamens 2-3.5 mm, of 3 abaxial ones (4-)5-9(-10) mm, the anthers of 4 median stamens (the anterior pair larger) 3-9 mm, their divaricate 2-porose beak 0.2-0.4 mm, those of 3 abaxial ones lunately incurved, the body 4.5-10 mm, the porrect beak 0.6-1 mm, its pores fully separated but sometimes only by a thin septum; ovary either strigulose or pilose, the vesture not correlated with that of stems or foliage; style filiform, sometimes lengthening after anthesis, then (4-)5-9(-10) mm, gently incurved distally and variably dilated; ovules (26-)30-50. Pod ascending, variably arched outward, narrowly linear 10-24 x 0.25-0.4 cm, at base attenuate into a scarcely differentiated stipe, at apex into the persistent style, the body compressed-quadrangular, bluntly bicarinate along each suture, these constricted only where ovules abort, the stiffly papery valves nearly plane, finely venulose lengthwise, strigulose or pilose (subtomentose), the interseminal septa 4-9 mm apart; seeds basipetally oriented along the pod’s long axis, obliquely quadrate-oblong 3-6.6 mm long, the testa smooth lustrous, the linear-oblong-elliptic areole 2-3 x 0.3-0.75 mm.
Variety Key - Key to the Varieties of S. pilifera 1. Stems either diffusely weakly ascending or prostrate and distally incurved, mostly 1.5-5, exceptionally to 10 dm; lf-rachis 7-15 mm; fls relatively large, the longest sepal 8-13 mm, the longest petal 24-36 mm; anthers of 3 abaxial stamens (excluding beak) (9-) 10-15 mm; seeds 5.5-6.6 mm long, the testa atropurpureous; around and within Gran Chaco and floristically related savanna regions in S. America s.-ward from lat. 24°S: s.-e. Bolivia, n.-w. and n.-e. Argentina, e. to the Parana-Paraguai slope of the Brazilian planalto, s. to e. Sao Paulo, centr. Parana, e. Rio Grande do Sul and Uruguay. 63a. var. pilifera (p. 243). 1. Stems erect or strongly assurgent (0.6-) 1-2.4 m; lf-rachis 3-6(-9) mm; fls smaller, either the long sepals 4.5-7.5(-8.5) mm or the longest petal (12-) 13-23(-26) mm, or both; anthers of 3 abaxial stamens 4.5-10 mm; seeds 3-5 mm long, the testa castaneous; allopatric, except for emphatically smaller-fld var. tubata. 2. Style only slightly dilated distally, widest shortly below apex, there 0.3-0.6 mm diam and thence contracted to a narrower, introrsely directed stigmatic cavity; lfts membranous, puberulent on both faces, obscurely reticulate dorsally; anthers of 3 abaxial stamens 6.5-10 mm; Mexico to Panama, n. Colombia, the Pacific slope in Ecuador, n. Peru; Cuba; disjunctly in n. & e. Venezuela and in e. Brazil from the Amazon delta s. to centr. Mato Grosso, Distrito Federal, s. Minas Gerais and e. S. Paulo. 63b. var. sub glabra (p. 243). 2. Style trumpet-shaped, distally dilated up to the suberect stigmatic cavity, this 0.7-1 mm diam; lfts glabrous on both faces and, when mature, coarsely reticulate dorsally (as var. pilifera); anthers of 3 abaxial stamens 4.5-5.5 mm; Andean foothills in Bolivia and local (riparian or weedy, possibly introduced) on the Parana and Paraguai rivers in Paraguay and s.-w. Brazil (Mato Grosso). 63c. var. tubata (p. 245).
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Discussion
As defined by Bentham (1870, l.c.), Cassia pilifera was inordinately polymorphic in stature, in pubescence, in outline, texture and venation of leaflets, in size of flower-parts, and in seeds. Bentham noted the more coriaceous, prevailingly broad leaflets of plants from southern Brazil, but dismissed this feature as systematically unimportant because it seemed not correlated with flower-size, which he found equally variable in South and North America. With more material for comparison, we can now perceive, to the contrary, strong relations between geographic dispersal on one hand and on the other phenetic characters of habit, leaf-texture, flower-size and seed which enable us to restore to varietal rank the taxon described long ago by Vogel as Cassia maritima, our var. sub glabra, now believed to be the only representative of S. pilifera in the northern hemisphere and to extend southward interruptedly in Brazil to the Amazon-Parana watershed. A form of the species resembling var. subglabra in most characters but with a greatly dilated, trumpet-shaped style and an allopatric range within that of var. pilifera can be segregated without difficulty as var. tubata.