Mimosa bonplandii (Hook. & Arn.) Benth.

Authors

Rupert C. Barneby

Authority

Barneby, Rupert C. 1991. Sensitivae Censitae. A description of the genus Mimosa Linnaeus (Mimosaceae) in the New World. Mem. New York Bot. Gard. 65: 1-835.

Family

Mimosaceae

Scientific Name

Mimosa bonplandii (Hook. & Arn.) Benth.

Synonyms

Acacia bonplandii Gillies ex Hook. & Arn., Acacia lepidota Hook. & Arn., Mimosa bonplandii var. minor Benth.

Description

Species Description - Unarmed, slenderly much branched, broad-crowned shrub or treelet 1-3 m, the annotinous and older defoliate branches dark reddish-brown, the young branchlets and lf-stks lepidote with contracted multiradiate stelliform setulae, the dull olivaceous subconcolorous lfts glabrous above, either glabrate or thinly weakly stellate beneath, the small globose or plumply ovoid capitula fasciculate in axil of coeval lvs, the fruits maturing on defoliate branchlets below the foliage. Stipules triangular-subulate or linear-attenuate 1-4 x 0.4-1 mm, 1 -nerved, deciduous. Leaf-stalks of primary lvs on flowerless stems ±2-4.5(-5.5) cm, of smaller simpler lvs associated wth fls ±1-2 cm, the petiole including hard insensitive pulvinus 5-11 x 0.3-0.6 mm, the longer interpinnal segments 2-9 mm, the shallow ventral sulcus bridged between pinnae but spicules 0; pinnae of lvs coeval with fls (l-)2-4-, of some larger primary lvs to 7(-9)-jug., the rachis of longer ones mostly 10-23 mm, of primary lvs to 40(-45) mm, the longer interfoliolar segments 0.5-1.6 mm; lfts of distal pinnae (9-)l 1-24-jug., scarcely graduated, the blades oblong to narrowly oblong-obovate or linear-oblong from obliquely truncate base, obscurely mucronulate at apex, the longer ones 2.5-5.5(-7) x 0.8-2(-2.2) mm, 2.6-3.4 times as long as wide, all veinless above, beneath weakly 1-nerved by scarcely excentric, immersed but discolored midrib. Peduncles (l-)2-5(-6) per axil, 2.5-11 mm; capitula without filaments (3.5-)4-5.5mm diam., prior to anthesis moriform, the obtuse fl-buds densely stellate, the receptacle 1.5-4 mm; bracts ovate-elliptic or lanceolate 0.7-1.2 mm, 1-nerved, glabrous or thinly stellate dorsally, persistent; flowers 4-merous 4-androus, most or all bisexual; calyx shallowly cup-shaped 0.4-0.5 x 0.7-0.9 mm, glabrous externally, the depressed-deltate, often unequal teeth minutely ciliolate; corolla campanulate 2-2.6 mm, the erect, shallowly concave ovate lobes 0.7-0.9 x 0.8-1 mm; filaments pale yellow, monadelphous through 0.8-1 mm and alternating with minute subulate staminodia, exserted 2-3 mm. Pods commonly 2-5 per capitulum, sessile but cuneate-attenuate at each end, in profile linear-moniliform, gently decurved, 10-36 x 4-5 mm, (l-)2-5(-6)-seeded, the deeply constricted replum 0.45-0.7 mm wide, the papery valves convexly dilated over each seed, the replum and valves alike densely pallid-stellate overall, the ripe valves breaking up into elliptic free-falling, individually dehiscent articles 4.5-7 mm long; seeds plumply obovoid, scarcely compressed, ±4.5 x 3.5-4 x 3.5 mm, the testa smooth, brown or dark brown, the embryo suspended in transparent endosperm between two air-cavities, the whole seed water-borne.

Distribution and Ecology - On beaches and riverbanks inundated at high tide, locally plentiful and sometimes forming thickets, below 25 m, common in the Paraná estuary and on the s. shore of rio de la Plata as far e. as Magdalena, prov. Buenos Aires, Argentina, of old reported from the banks of lower Uruguai in Uruguay and collected recently upstream near Paso de los Libres in prov. Corrientes, Argentina, to be sought on the left bank of the Uruguai in extreme s.-w. Rio Grande do Sul, Brazil.—Fl. VII-XII, the fruit persisting into I-III.

Discussion

Nothing of substance can be added to the discursive accounts of M. bonplandii provided by Burkart (ll.cc.), who first described the riparian ecology of the species and its buoyant seeds. The only member of sect. Calothamnos that shares the habitat and, in part, the range of M. bonplandii is M. pilulifera, readily distinguished by unijugate pinnae of all leaves and by filaments free to the base, without intervening staminodia.

Distribution

Argentina South America| Corrientes Argentina South America| Uruguay South America| Brazil South America| Rio Grande do Sul Brazil South America|