Senna cumingii (Hook. & Arn.) 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. cumingii indicatur.
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Synonyms
Cassia cumingii Hook. & Arn.
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Description
Species Description - Shrubs variable in habit, either erect or diffuse, then bushy and sometimes wider than tall, at anthesis (0.3-)0.6-3 m, the old bark dark gray, the annotinous branchlets, lf-stalks and axes of inflorescence puberulent or pilosulous with forwardly subappressed-ascending, mostly straight or simply incurved, pallid lutescent hairs of variable length, the longest up to 0.1-1.1 mm, the dull olivaceous foliage subconcolorous, the lfts firm when mature, minutely or conspicuously ciliolate, usually glabrous on upper face but rarely puberulent along midrib, the dorsal face either glabrous or sparsely pilosulous, the inflorescence of leafy-bracteate racemes sometimes at first lateral but eventually or from the first forming a shortly exserted subcorymbiform panicle. Stipules erect, thinly herbaceous, linear-lanceolate, linear, linear-attenuate or subulate (1-)2-10(-12) x 0.2-0.8 mm, deciduous before the lf but not precociously caducous. Lvs (3.5-)4- 12 cm; petiole including the scarcely swollen pulvinus (2.5-)4-16 mm, at middle 0.4-1 mm diam, bluntly 3-ribbed dorso-laterally, the shallow, narrowly thick-margined ventral sulcus narrow or closed; rachis (2-)2.5-6.5(-8) cm; gland (much eaten) between proximal pair of lfts shortly stipitate or subses- sile, in profile 0.7-1.6 mm, the ovoid acute or fusiform body (0.l-)0.2-0.5 mm diam, rarely a similar gland between second pair; pulvinules (0.5-)0.6-1.2(-1.5) mm; lfts 4-7(-8) pairs, highly variable in length and width, at narrowest linear- acuminate, at broadest obovate obtuse or emarginate, usually little or not at all accrescent distally, the outline, dimensions and venation described under the vars., the venation in general subsimply pinnate with 2-5 pairs of camptodrome secondary veins prominulous on both faces or only beneath, the margin plane or incipiently revolute near the pulvinule. Racemes mostly (5-)6-13, some rarely to 30-fld, the usually 2 or more simultaneously expanded fls raised ± to level of the nodding obovoid glabrous or proximally puberulent buds, the axis together with peduncle becoming 5-10(-14) cm; bracts submembranous, narrowly lance-elliptic, linear-attenuate or subulate (1.5-)3-9(-l 1) x 0.4-1(-2) mm, deciduous by or shortly before anthesis; mature pedicels (9-) 11-26 mm; sepals usually fuscous or purplish with broad pallid or petaloid margins, delicately immersed-venulose, oblong-obovate or -elliptic obtuse, a little graduated, the longer inner ones 6-11.5(-12) mm; petals glabrous, rich golden- or orange-yellow, when dry remaining yellow brown-venulose, of subequal length but the vexillar one broadest, its blade flabellate-emarginate, the rest a little narrower obovate or broadly oblanceolate in outline, the longest petal 9-26 mm; androecium glabrous, the 3 cordate staminodes 1.4-1.9 mm wide, the filaments of 4 median stamens (1-) 1.2-1.8 mm, of 2 long abaxial ones 5-17 mm, of the centric abaxial one 2-3.5 mm, the anthers of 4 median stamens 3.2-5 mm, of 2 long abaxial ones (4.5-)5-7.6 x 1-1.6(-1.7) mm, of the sterile centric abaxial one 1.5-7 x 0.2-1 mm, the fertile anthers all subhorizontally truncate or the orifice of the 2 longer ones obliquely dilated into an obscure pollen-cup up to 0.4 mm; ovary pilosulous or strigulose; style 2-9.5 mm, not or scarcely dilated upward, ±0.2-0.35 mm diam at gently incurved apex; ovules 10-24. Pod at first obliquely ascending, in age randomly declined, the stipe 2.5-6 mm, the straight or slightly decurved linear or linear-oblong body 4-10 x 0.6-1.1 cm, commonly strangulate at some abortive locules, compressed but when ripe turgidly expressed over the seeds, the green valves becoming stiffly papery and when ripe pale brown, broadly paler-margined along each suture, the interseminal septa well developed, the locules 4.5-9 mm long; seeds plumply disciform or oblong-obovoid, 4.6-7.2 x 4-6.3 mm, usually compressed parallel to the valves but when crowded into narrow locules becoming obtusely 4-angular, the dull brown or blackish testa smooth, the broadly elliptic or circular areole 3-5.5 x 2-5 mm.
Variety Key - Key to the Varieties of S. cumingii 1. Fls relatively small, the longest petal 9-16 mm; filaments of 2 long abaxial stamens 4.5-8.5 mm; style 2-5 mm; pod (at fertile segments) ±6-9 mm wide; ovules 10-16. 2. Lfts of major lvs linear-lanceolate or -elliptic, the longer ones ±20-35 x 3-7 mm and 4-10 times as long as wide; style 2-3 mm. 98a. var. cumingii (p. 314). 2. Lfts of major lvs either of broader outline or shorter, or both.3. Major lfts at once short and broad, ±12-16 x 3.5-5.5 mm; style ±2 mm; local between 25° and 25°30'S in Antofagasta. 98b. var. eremobia (p. 314). 3. Major lfts up to 23-32 x 7-10 mm; style 4-5 mm; Coquimbo. 98c. var. alcaparra (p. 315). 1. Fls larger, the longest petal 15-26 mm; filaments of long abaxial stamens 10-17 mm; style 5-9.5 mm; pod 9-11 mm wide; ovules 16-24; Coquimbo. 98d. var. coquimbensis (p. 315).
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Discussion
Our concept of S. cumingii is expanded here over that of Cassia cumingii sensu Bentham so as to absorb without strain C. coquimbensis Vog., C. eremobia Phil, and C. alcaparra Phil., as well as the long-established synonyms C. flaccida Clos and C. acuta Meyen ex Vog. Each of these was described originally from one or few individual plants which now fall into place as points along a sequence of vicariant variations; while different in relative amplitude of foliage, in flower size, in length of long filaments and in ovule-number, the constituent elements of the species are held together by an essentially uniform androecium, pod and seeds, and by a continuous range in arid Pacific extratropical Chile. The process of assembling these under one specific title began with the protologue of C. cumingii itself, where Hooker & Arnott listed as an unnamed variety the first collection of what would later be segregated by Philippi as C. alcaparra. More recently Johnston has voiced the suspicion that C. eremobia is no more than a northern variety of C. cumingii. The steps leading from C. alcaparra, which has almost as ample leaves but a rather shorter style, to large-flowered dolichostylous C. coquimbensis on the one hand and to small-flowered brachystylous narrowleaved C. cumingii are equally short and easy. The close affinity of S. cumingii sens. lat. seems to lie with the high Andean or trans-Andean S. versicolor and S. arnottiana which have very similar pods and seeds. The former differs in the mostly 8-13 (not 4-8) pairs of leaflets characteristic in color; the latter in the succulent foliage and dwarf stature. Senna birostris, of which two varieties are adapted to arid coastal hills ecologicially similar to the preferred habitat of S. cumingii, differ at once in leaflet-number, broader pods and unmarked seeds.
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Common Names
Alcaparra