Senna morongii (Britton) H.S.Irwin & Barneby

Authors

Howard S. Irwin, Rupert C. Barneby

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.

Family

Caesalpiniaceae

Scientific Name

Senna morongii (Britton) H.S.Irwin & Barneby

Type

Holotypus (2 sheets, fl, fr), NY!

Synonyms

Cassia morongii Britton, Cassia tomentosa var. paucijuga Kuntze, Cassia rojasiana Hassl., Cassia acinacicarpa Rusby, Cassia cochabambae Herzog

Description

Species Description - Slender, amply leafy shrubs at anthesis ± 1-2 m, with terete virgately ascending hornotinous and brown lenticellate older branches, pilosulous or tomentulose throughout with widely spreading straight or incurved or with mostly antrorsely incumbent hairs up to 0.4-1 mm, the foliage dull pale green or commonly softly gray-woolly (the vesture often sordescent when dried), the lfts subequally pubescent on both faces but commonly paler beneath, the shortly pedunculate few- fld racemes shorter than the subtending lf, lateral to annotinous stems or their secondary branchlets, rarely in age forming a small semi-exserted panicle. Stipules loosely ascending, narrowly lanceolate or lance-attenuate (1.5-)2-4.5 x 0.3-0.8 mm, at first herbaceous, quickly dry caducous, often before full expansion of the associated lf, absent from all but young flowering spms. Lvs (4-)5.5-13(-14.5) cm; petiole (8-)10-22(-24) mm, at middle (0.5-)0.6-1.1 mm diam, strongly pale-margined along the narrow ventral sulcus; rachis (1 -2-) 1.5-6(-9) cm, the longer interfoliolar segments (8-) 10- 18(-25) mm; petiolar gland between the proximal pair of lfts sessile or obscurely stipitate, the green or orange head slenderly or plumply ovoid acute or apiculate, in profile 0.7-1.4 x 0.3-0.7 mm; pulvinules 0.6-1.4 mm; lfts 2-5, in most lvs of any plant 3-4 pairs, accrescent and proportionately narrower distally, the distal pair longest, obliquely lanceolate or lance-elliptic, either acute or obtuse and apiculate, 2.5-6 x (0.5-)0.6-1.6(-1.8) cm, (2.9-)3-5 times as long as wide, at base rounded or cordate on proximal and cuneate on distal side, the (mature) margin revolute, the upper face of blade veinless or almost so, the midrib prominulous beneath only, there giving rise to 4-7 pairs of slender, weakly camptodrome secondary veins, tertiary venulation invisible and all venation commonly obscured by vesture. Peduncles slender (5-)8-21(-24) mm; racemes shortly or subumbellately (l-)2-6(-10)-fld, the axis becoming 1.5-10(-30) mm and together with peduncle in fruit 1-3.5(-4.5) cm; bracts lance-subulate, early dry caducous from below incipiently elongating pedicel; fl-buds obliquely obovoid-ellipsoid obtuse pilosulous when young, the emergent inner sepals often glabrescent dorsally; hypanthium turbinate ±1-1.5 mm; sepals moderately graduated, the outer firm, the shortest 3-4.4 mm, the inner broadly elliptic-obovate, pallidly membranous-mar- gined (4.5-)5-7 mm; corolla zygomorphic, the yellow petals drying paler yellow or stramineous, delicately dark-veined, glabrous or puberulent at the short claw, the vexillar one obovate-emarginate, its 2 neighbors obovate obtuse, the 2 abaxial ones elliptic or lance-elliptic, often a trifle longer than the anterior ones, the longest 7-11 (-11.5) mm; androecium glabrous or puberulent about the filaments, functionally 7-merous, the oblong or rhombic, basally cordate blade of the staminodes 1-1.3 mm wide, the filaments of 4 median stamens 0.5-1.6 mm, of the centric abaxial one 2-4 mm, of 2 latero-abaxial ones dilated 3.5-6 mm, the anthers brownish yellow-tipped, of 4 median stamens straight 3.5-4.5 x 0.7-1.2 mm, of the centric abaxial one 4-6 x 0.7-1 mm, of the long pair lunately incurved 5-6.8 x 1-1.2 mm, all anthers slightly constricted 0.4-0.6 mm below apex, those of 4 median stamens there obliquely, of the rest horizontally truncate, the latter dehiscent by a broadly U-shaped pore, the orifice of the 4 median often divided by a persistent septum; ovary pilosulous, usually densely and loosely so; style glabrous or proximally puberulent, incurved from ovary thence straight, linear slightly dilated upward (1.8-)2-3.3(-3.5) x 0.2-0.3(-0.4) mm, the minute stigmatic cavity looking upward; ovules (52-)56-86. Pod stiffly obliquely geotropic (sometimes apparently ascending from geotropic branches), the stipe 4-6 mm, the cylindric or subtetragonally compressed, straight or gently incurved body 6-8.5 x (0.5-)0.6-0.9(-l.l) cm, abruptly contracted at both ends, sometimes obscurely sulcate along one or both of the broadly margined sutures, the pilosulous green valves in age brunnescent or stramineous and stiffly papery, not or scarcely pulpy internally, the individual, completely enclosed seed-cavities 2-2.8 mm long, occupying ± half the width of the pod; seeds transverse, stacked in 2 parallel or very shallowly interdigitating rows, each turned with broad faces to the septa, in outline obliquely obovate (2.9-)3.3-4.6 x (2-)2.7-3 mm, the testa fuscous or brownish-olivaceous smooth and highly lustrous, exareolate.-Collections: 47.

Distribution and Ecology - Rocky hillsides, thickets, riverbanks and beds of intermittent streams, mostly extratropical and ranging between 350 and 1200 m along the Andean piedmont in n.-w. Argentina from Jujuy s. to centr. Cordoba and n. San Luis, thence extending e.- and downward to 100 m, mostly along rivers, over Gran Chaco to the Paraguay Valley in s. Paraguay and adjacent Argentina (Corrientes); apparently isolated near 2000-2700 m on the headwaters of the Rio Grande in Cochabamba, Bolivia.—Fl. XI-V(-VIII), the long-persistent pods often coeval with fls.

Discussion

Senna morongii is easily distinguished from kindred species with cylindric pod and biseriate seeds by the relatively few, most commonly 3-4 pairs of leaflets veinless on the upper face and pilosulous-tomentulose on both. The vesture varies in length, attitude and concentration of hairs, but we cannot recognize any geographic pattern to it. The synonymy, worked out by Burkart (1952), is accountable to duplication of effort rather than critical differentiation.

Common Names

pito, p. canuto, algarrobo de los caranchos, sen

Distribution

Jujuy Argentina South America| Córdoba Argentina South America| San Luis Argentina South America| Corrientes Argentina South America| Cochabamba Bolivia South America| Paraguay South America|