Mimosa bimucronata (DC.) Kuntze
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Authors
Rupert C. Barneby
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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.
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Family
Mimosaceae
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Scientific Name
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Type
89. Mimosa bimucronata (DeCandolle) O. Kuntze, Revis. gen. pl. 1: 198. 1891.—Typus infra sub var. bimucronata indicatur.
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Description
Species Description - Trees and bushy treelets (2-)3-8(-10) m, armed along new leafy branches and on random lf-stks with stout intemodal aculei 1—8(—10) mm, but the purplish-brown flowering branchlets and their lf-stks usually unarmed or nearly so, the new stems with lf-stks (especially ventrally) and axes of exserted paniculate inflorescence densely or quite thinly puberulent with erect-ascending sordid or yellowish hairs to 0.2-0.4 mm mixed with few or many livid granules, the firm plane concolorous lfts olivaceous and moderately lustrous on both faces, often minutely ciliolate, the widely branched panicle of small white capitula leafless or almost so, exserted (1-) 1.5-4 dm from foliage. Stipules firm erect-incurved, narrowly or broadly lanceolate 2-5 x 0.7-1.3 mm, concave ventrally, pubescent within and without, persistent. Leafstalks 4-9(-l 1) cm, the petiole including elongate livid pulvinus 7-24(-30) x 0.8-1.4 mm, the longer interpinnal segments 7-16 mm, the deep ventral groove interrupted between pinna-pairs by a pubescent bridge sometimes surmounted by a conic or subulate spicule; pinnae (3-)5-9(-10)- jug., a little decrescent proximally, the rachis of longer ones 3.5-6.5(-7) cm, the longer interfoliolar segments (1.2-) 1.4-2.5 mm; lfts of longer pinnae (16-)24-32-jug., a little decrescent at each end of rachis, the first pair 1-1.8 mm distant from reflexed subulate pubescent paraphyllidia, the blades linear or linear-oblong from obliquely dilated base, acute or apiculate at apex, straight or slightly arched forward, the longer ones 6.5- 10(—14) x l.l-2.3(-4.5) mm, all veinless above, the dorsally prominulous costa dividing blade ±1:2 and giving rise on each side to 1-3 weak secondary venules. Peduncles 1—3(—5) per node of inflorescence, 6-16(-20) mm; capitula globose, without filaments (4.5-)5-6 mm diam., prior to anthesis moriform, the obtuse fl-buds glabrous or minutely papillate; bracts obovate-cuneate or spatulate 0.4-0.7 mm; flowers white fragrant 4(randomly 5)-merous diplostemonous, the pistil of some lower ones often rudimentary; calyx campanulate 0.55-0.9 mm, the sometimes obscure teeth 0.05-0.15 mm; corolla vase-shaped 2-2.8 mm, the ovate 1-nerved, nearly plane lobes 0.8-1.1 x 0.6-0.8 mm, sometimes minutely papillate around margin distally; filaments white, free, exserted 4.5-6 mm; ovary usually glabrous, sometimes minutely resinous-papillate. Pods 1-5 per capitulum, in profile broadly linear, straight or gently decurved, planocompressed, the body when well fertilized 35-60(-70) x 5.5-7.5 (teste Burkart, 1948, -9) mm, at base cuneately contracted into a stipe 1.5-5 mm, the replum almost straight (except where ovules abort), 0.5-0.6 mm diam., the papery reddish-brown, finally nigrescent, glabrous but sometimes granular valves scarcely elevated over seeds, when ripe separating from replum and breaking up into (4-)5-8(- 9) transversely oblong or almost square articles 5-7 mm long; seeds rhombic-elliptic in wide profile, 3.7-5.5 x 3-4 mm, strongly compressed, the testa dull fawn-olivaceous girdled by fuscous margin.
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Discussion
In its Brazilian range the well-known M. bimucronata varies little. Some herbarium specimens, due to the size of the inflorescence, include only depauperate leaves at or near base of the panicle, which may give a misleading picture of the potential leaf-formula. Others show only unarmed branchlets, but aculei are believed to be regularly present on some part of the plant. The status of the Paraguayan var. adenocarpa, in which the lfts appear at once fewer and much wider, remains uncertain, but it is provisionally retained here in order to stimulate further studies. Burkart interpreted var. adenocarpa (in annotation of Fiebrig 4770, P) as equivalent to M. hexandra, but its flowers are tetramerous and the immature pod shows no sign of suberous thickening.
The abundant, sweetly fragrant white flowers of M. bimucronata are a source of honey, and its hard wood is used in carpentry and cabinet-work. Its long-established use in southeastern Brazil as a hedge is acknowledged in Bentham’s epithet sepiaria. It is used in folk-medicine (Pio Correa, 1931) to treat asthma and intermittent fevers.