Senna splendida
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Title
Senna splendida
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Authors
Howard S. Irwin, Rupert C. Barneby
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Scientific Name
Senna splendida (Vogel) H.S.Irwin & Barneby
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Description
44. Senna splendida (Vogel) Irwin & Barneby, comb. nov. Cassia splendida Vogel, Syn. Gen. Cass. 17. 1837.—Typus sub var. splendida indicatur.
Weak, diffuse or ascending shrubs and slender, commonly sarmentose treelets at anthesis (1-)2-6(-10) m, except for always strigulose ovary and often dorsally puberulent petals and pedicels wholly glabrous, or the stems and lf-stalks exceptionally thinly incumbent-pilosulous, the young branchlets smooth subterete, the foliage bicolored, lustrously olivaceous above, paler dull beneath, the thyrsiform- paniculate inflorescence mostly leafy-bracteate, or by atrophy of some distal lvs shortly exserted.
Stipules usually falcate linear-oblanceolate or oblanceolate (5-)7- 20 x (0.5-)0.7-5 mm, rarely dilated and obliquely obovate-cuneate to 10 mm wide, caducous, present at base of young lvs but lacking from many mature specimens.
Lvs (5-)6-13(-15.5) cm (some distal ones smaller); petiole including wrinkled but little dilated pulvinus (8-)10-35(-42) mm, at middle (0.4-)0.5-0.9(-l) mm diam, bluntly low-carinate dorsally, shallowly grooved ventrally; rachis (4-)6-18(-21) mm, shorter than petiole; seta filiform persistent or deciduous; gland 1 inserted immediately above lower pair of pulvinules, clavi- or linguiform stipitate, in profile 1.5-4.5(-5) mm tall, the ovoid or narrowly lance-ellipsoid body decurrent around sides of the ventrally sulcate stipe and either longer or shorter than it; pulvinules discolored wrinkled 1.3-3.2(-3.5) mm; distal pair of lfts ovate to lance-elliptic, elliptic, or seldom linear-elliptic, obtuse or subemarginate, often minutely mucronulate, of larger lvs (4-)5-10.5 x (1.2-) 1.5-3.5(-3.8) cm, mostly 2-4 times, when linear-elliptic 4-6.5 times as long as wide, at base subsymmetrically rounded on both sides or broadly cuneate on the distal one, the entire margin either plane or re volute, narrowly sharply membranous-margined, the slender straight midrib giving rise on each side to (9-)l 1-19(-24) major camptodrome and ± as many intercalary widely ascending secondary veins, these all with the tertiary venulation finely prominulous on both faces, the reticulation of the lower face carried out to areoles <0.5 mm diam.
Peduncles with raceme-axis (0.7-)l-7 cm; racemes (1-)2-10(-12)-fld, the fls subumbellate when few, racemose when over 3; bracts ovate or lanceolate obtuse or acute 2-5(-6) mm, persistent into anthesis, then deciduous; pedicels at and after full anthesis 2-4.5 cm; buds either obtuse or acute; sepals submembranous, olivaceous, fuscous, red-flecked internally, or dull red, glabrous dorsally, hetero- morphic either in length or shape (described in varietal key), the longest inner ones oblong-oblanceolate to suborbicular (8.5-) 10-30 mm; petals yellow short- clawed, heteromorphic, 1 adaxial flabellate-emarginate or obcordate, 2844 x (16-)20-33 mm, the rest varying from broadly obovate to oblanceolate obtuse, narrower than the adaxial one but either a little longer or shorter, one abaxial one oblique; filaments glabrous, those of (2-)3 abaxial stamens (4-)7-12.5 mm, the one furthest from the oblique petal shorter, those of 4(-5) median ones 2.5-4 mm, the thecae glabrous, of 3 long stamens 11-17 mm with porrect beak (1-) 1.2-2.3 mm, of 4 median ones 5.5-9(-10) with divaricate-appressed beak 0.45-1.2 mm, the pores confluent; ovary gray-strigulose, quickly elongate-vermiform after fertilization, the short glabrescent style 0.6-0.9 mm diam just below the oblique stigmatic cavity, this 0.2-0.5 mm diam; ovules 160-240.
Pod pendulous stipitate, the stipe 10-17 mm, the teretely subcylindric body 17-36(-49) cm, constricted only where ovules abort, 8-13(-15) mm diam, the thin, finally papery and lustrous valves green turning brown, smooth or faintly transverse-venulose; dehiscence tardy, along ventral suture; seeds (little known) either 1- or 2-seriate, turned broadside to the septa, compressed-pyriform 5-6 mm, the testa castaneous lustrous, exareolate.
Among large-flowered Bacillares with strongly dimorphic sets of fertile stamens the appropriately named S. splendida is readily recognized by its relatively small ovate- or lance-elliptic, bilaterally subsymmetrical leaflets prominently but finely venulose with widely ascending secondary veins and thence delicately reticulate. The leaf-blades vary considerably in outline, but the relatively uncommon forms with narrowly lance-elliptic leaflets, Bentham’s var. angustifolia, are of sporadic occurrence in the southern half of the whole range of the species and are not sharply distinguished morphologically. On the other hand a marked variation in the sepals, with consequences in the outline of the flower-buds, is definitely linked with north-south dispersal and deserves taxonomic notice. The extremely long and narrow multiovulate pod of S. splendida elongates with great rapidity after fertilization, its length finally accommodating the seeds in either one or two rows. It has been collected only rarely in fully ripe condition and it is too early to say whether the arrangement of the seeds is taxonomically significant or not.
The neat foliage and large lustrous golden flowers of S. splendida will recommend it to tropical gardeners who have place for an ornamental vine that can be trained to a pergola or planted so as to scramble through small trees. In Brazil it has been used most effectively as a free-standing round-headed tree in city parks.
Key to the Varieties of S. splendida
1. Sepals at once strongly graduated and all obtuse, the 2 outermost broadly obovate-suborbicular 5-10(-11) mm, 1/4-2/3 as long as the long inner ones; fl-buds subglobose, very obtuse.
44a. var. splendida (p. 191).
1. Sepals not strongly graduated but differentiated in shape, the outer lance-acuminate with recurving tips, (16-) 18-28 mm, nearly as long as the obtuse inner ones; fl-buds ovoid-apiculate or -acuminulate.
44b. var. gloriosa (p. 192).