Monographs Details: Mimosa macropogon Barneby
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
Synonyms:Mimosa piresii Barneby
Description:Species Description - Amply macrophyllidious shrubs, unarmed and eglandular, including the far-exserted efoliate panicle of small globose capitula attaining 2-5 m, the stout terete stems and lf-axes at once puberulent and hispid with slender erect rufous setae to 7-13 mm and at base 0.1-0.3 mm diam., the fresh stems resinous (staining drying papers), the axes of panicle puberulent and much more shortly setulose, the stiffly papery, when dry dull brown lfts palmately venose and reticulate, the panicle at least 4 and to 11 dm long (not seen entire) with longer branches to 2-3 dm. Stipules stiffly foliaceous erect, broadly lanceolate or triangular, to 1.5-3.5 cm long, densely ascending-setose dorsally, persistent. Leaf-stalks to ±17-30 cm, near base 3-6 mm diam., the petiole and interpinnal segments 4.5-6.5 cm, the terminal appendage lance-caudate 1.5-2 cm; interpinnal spicules not seen; pinnae 4-5-jug., the laterally compressed rachis of distal pairs 15-17.5 cm, the longer interfoliolar segments 3-5.5 cm; lfts 6-7(-8)-jug., only a little decrescent at each end of rachis, the first pair ± 15-20 mm distant from grossly dilated livid pulvinule (paraphyllidia 0), the blades obliquely ovate from inequilateral cordate base, broadly obtuse or shallowly emarginate and mucronulate at apex, plane-margined, the longer ones attaining 4-7 x (2-)2.5-4 cm, all flabellately 7-9-nerved from pulvinule, the straight midrib dividing blade ±1:2, several-branched upward from below middle, the inner of two anterior primary nerves and the inner posterior one incurved and brochidodrome beyond mid-blade, the outer ones weaker and shorter, all primary and secondary nerves further branched into an open reticulum bluntly prominulous on both faces, but a little more sharply so beneath than above. Peduncles 2-4 per node, to 10-22 mm, ebracteolate, each fascicle subtended by a pair of ovate, dorsally setulose deciduous bracts; capitula without filaments 5-6 mm diam., prior to anthesis moriform, the fl-buds densely setulose; bracts oblong less than 1.2 mm, setulose externally; flowers 4-merous 8-androus, at least some lower ones staminate; calyx pappiform 1.1-1.4 mm, the shallowly campanulate tube 0.4-0.45 mm, densely silky-strigulose externally, the rim densely setose-ciliate; corolla turbinate 2.6-2.8 mm, the ovate cymbiform but scarcely thickened lobes 0.9 x 0.6 mm, densely sericeous dorsally; filaments cream-white, monadelphous through 0.5-0.65 mm, exserted ±6 mm; anthers 0.35 mm diam.; style longer than stamens. Pods narrowly linear in profile 60-80 x 8 mm, 8-12-seeded, contracted at base into a stipe 2-4 mm, the replum 0.4-0.5 mm wide, the brown papery valves low-convex over each seed, glabrous, transversely venulose, breaking up when ripe into free-falling indehiscent articles 6-7 mm long.

Distribution and Ecology - In savanna at low elevations, locally common in the middle Madeira basin near 62°-63°W in s.-e. Amazonas (mun. Humaitá; rio Marmelos) and adj. T. F. Rondônia, Brazil.—Fl. VII- VIII(-?).

Discussion:

Mimosa macropogon is related closely only to the ecologically similar M. piresii but is notably different in the extremely large stipules and reticulately venose leaflets, the indumentum of extremely long cauline setae, and the externally setulose calyx.

Distribution:Brazil South America| Rondônia Brazil South America| Amazonas Brazil South America|