Senna tapajozensis (Ducke) 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
Lectoholotypus, R. 16990, R!
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Synonyms
Cassia tapajozensis Ducke, Cassia chrysocarpa var. macrocarpa Benth.
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Description
Species Description - Weak, softly woody shrubs, in open places diffusely ascending or trailing, in brush or forest-savanna ecotone becoming sarmentose with drooping or pendulous branchlets, at anthesis 1-3 m, strigulose-pilosulous throughout with fine incurved, widely spreading or (on lvs) forwardly appressed hairs up to 0.1-0.25 mm, the angulately ribbed hornotinous stems commonly densely so, often sub- velutinous, the thinly chartaceous lfts moderately lustrous dark green above, dull but little paler beneath, puberulent on both faces, the always minutely pilosulous inflorescence variable in form, usually thyrsiform and leafy-bracteate, sometimes paniculate, the uppermost lvs sometimes much reduced and the distal fls then becoming well exserted. Stipules subulate or linear-setiform, straight or falcate, 2.5-7 mm, at base 0.3-0.6 mm wide, caducous and often lacking from flowering spms. Adult cauline lvs (4-)7- 13(-14.5) cm; petiole including wrinkled but not much dilated pulvinus (1.2-)2-5.2 cm, at middle (0.7-)0.9-1.5 mm diam, shallowly open- grooved ventrally; rachis (3-)4-14 mm, much shorter than petiole, gland 1 sessile immediately above proximal pair of pulvinules, in profile broadly or narrowly lanceolate 3-5(-6) mm tall, a little dorsoventrally compressed, sulcate ventrally; pulvinules 2.5-5 mm, lance-cylindric, wrinkled when dry ; distal pair of lfts abruptly divaricate through ±90° from lf-stalk, in outline obliquely obovate obtuse to obliquely ovate-subrhombic or -elliptic short-acuminate, (2.5-)3.5-8.5 (-10) x (1.5-)2.2-4.5 cm, 1.4-2.2 times as long as wide, at strongly asymmetric base broadly rounded to cordate on proximal side, cuneate to narrowly cordate on the distal one, the margin (adult) revolute, the ± excentric, usually incurved midrib immersed above, carinate beneath, giving rise on each side to (5-)6-9 major camptodrome with or without intercalary secondary nerves, these and the tertiary connecting venules prominulous on both faces but often more strongly so beneath, the areoles of ultimate pronounced reticulation variable in size, the larger either > or <1 mm diam, the proximal pair of lfts ±1/3 shorter than the distal, proportionately broader, at base broadly and often deeply cordate on proximal side. Peduncles together with raceme-axis (1-)2-5 cm; racemes (2-)3-7(-10)-fld; bracts ovate or elliptic-oblanceolate concave 2-4 mm, caducous from young buds; pedicels at and after anthesis (13-)18-32(-37) mm; buds globose, densely pilosulous; sepals firm, the outer greenish or fuscous suborbicular 10.5-14 mm, even in late bud imbricate over the rest, the inner subpetaloid broadly obovate-orbic- ular very obtuse 12-17 mm; petals waxen yellow or orange-yellow, puberulent dorsally along the strongly elevated nerves, the 3 adaxial usually flabellate beyond slender claw, obtuse or emarginate (22-)24-32 mm, the 2 abaxial either a little longer or shorter but usually narrower, one obliquely incurved over 2 or 3 long stamens; filaments puberulent, those of 4 short fertile stamens 1.8-3.5 mm, of 3 abaxial long ones (3.5-)4-8 mm; thecae glabrous, those of 4 short stamens 6-9.5 mm, the divaricate beak 0.9-1.5 mm, those of 3 long ones 8.5-11, the erect narrowly conic beak 1.1-2 mm; ovary densely pallid- or yellow-sericeous; style 2-3.5(-4) mm, glabrate distally, near apex ±0.6-1.3 mm diam, the ciliolate orifice 0.3-0.55 mm diam; ovules 180-220. Pod pendulous, shortly stipitate, the stout stipe 4-12 mm, the straight or slightly incurved subterete body 14-33 x 1-1.4 cm, the valves becoming dark brown, glabrescent, coarsely but not very prominently venulose; seeds biseriate, turned broadside to the septa, clad in thin pulp, in outline obliquely or sublunately oblong-ellipsoid 4-5 x 2.2-3 mm, the brilliant castaneous testa cross-crackled, indistinctly areolate.—Collections: 34.
Distribution and Ecology - Forest margins in sand or clay soils on terra firme, s.-ward entering cerrado, in the Hylaea becoming locally abundant in capoeira and along highways, 25-450 m, scattered over w.-centr. Brazil on the middle Amazon-Solimoes river and its southern affluents, in w. Para on Rio Tapajos and in Amazonas upstream from mouth of Rio Maues, thence s. through the basins of the Jurua, Purus and Madeira into Acre and Rondonia, and s.-e. around the periphery of the Amazon basin to the Juruena-Paraguay divide and upper Xingu in centr. and n.-e. Mato Grosso; apparently disjunct on the coastal plain of Terr. Amapa.—Fl. (III-)IV-VII, fr. V-X.
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Discussion
Senna tapajozensis has the general appearance and growth-habit of S. chrysocarpa, but the strongly dimorphic fertile stamens of S. angulata. It was first provisionally described, from fruiting specimens, as a variety of S. chrysocarpa, a member of Bentham’s original series Bacillares, although the androecium is that of his ser. Speciosae. An exaggerated inequality between two sets of fertile stamens has probably evolved more than once in ser. Bacillares sens, lat., for ser. Speciosae Benth., degraded by Bentham himself in his monograph (1871, p. 524) to an informal infraserial category, appears a heterogeneous group. For differences between S. tapajozensis and S. angulata, see discussion of the species next following.
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Distribution
Pará Brazil South America| Amazonas Brazil South America| Mato Grosso Brazil South America| Amapá Brazil South America|