Monographs Details: Mimosa discobola 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.
Description:Species Description - Virgately erect, amply leafy unarmed subshrubs 10-18 dm, glabrous except for rare, vestigially or remotely appressed-setulose lf-axes, pulvinules, or bracts of inflorescence, the stout smooth substriate, minutely black-dotted stems at base fistular and to 5-6 mm diam., foliate to middle or beyond, thence passing into a simple pseudoraceme or a narrow thyrsiform or pyramidal panicle of proportionately small capitula, the stems and concolorous lvs when dry purplish-brown subglaucescent, the thick-textured but thin-margined lfts dull on both faces, veinless above. Stipules caducous, none seen. Leaf-stalks (3-)4.5-l 1 cm, the petiole including grossly dilated nigrescent pulvinus (1.5-)2.5—6 cm, at middle 0.7-1.1 mm diam., the interpinnal segments (8-) 10-20 mm, the open ventral groove continuous, spicules 0; pinnae (l-)2-4-jug., subequilong or the proximal pair shorter, the axis including livid wrinkled pulvinus (3.5-)4-8 cm, the longer interfoliolar segments 4-6 mm; lfts of longer pinnae 10-15-jug., the small first pair 2.5-5 mm distant from minute triangular-subulate caducous paraphyllidia, the rest subequilong, the blades obliquely oblong-elliptic from obtusely semicordate or simply obtusangulate base, obtuse at apex, the larger ones 8-12 x (2.2-)2.5- 5.5 mm, 2.1-2.4 times as long as wide, on dorsal face weakly 5-6-nerved from pulvinule, the straight midrib displaced to divide blade 1:22.6, the single anterior and 3-4 posterior nerves expiring within the margin, unbranched. Peduncles solitary, mostly 1-3 cm, some distal ones shorter; capitula globose, without filaments 5-6 mm diam., prior to anthesis moriform; bracts linear-oblanceolate 1.2-1.6 x 0.3-0.4 mm, shortly ciliolate distally, shorter than the glabrous, obtusely 4-angulate fl-buds; flowers 4-merous 4-androus, some lower ones staminate; calyx paleaceous 1-1.5 mm, cleft to or below middle into four deeply decompound lobes; corolla 2-2.5 mm, tubular-funnelform, the narrowly oblong cymbiform subacute corneous lobes 0.8-1 x 0.4-0.5 mm; filaments pink-lavender, free to base, exserted ±3 mm; ovary glabrous. Pods 1-3 per capitulum, subsessile at cuneate base, lomentiform piano-compressed 1.5—4.5 cm, consisting of 1-3 (-4) disciform round or broadly elliptic glabrous articles 9-13 mm in greatest diam. separated by isthmi 2-6 mm wide subequally indented from each suture, the narrowly ribbonlike replum 0.6-0.9 mm wide, the articles separating from it when ripe and falling as individually indehiscent 1-seeded achenes, the lustrous brownish-stramineous or livid-castaneous, delicately venulose valves at middle of each article low-colliculate over the seed and ±0.1 mm thick in section, thickened toward the margins; seeds discoid ±7.5 x 6 mm, the testa dull brown, but fuscous within the pleurogram.
Distribution and Ecology - In cerrado, apparently local about the watershed of rios Araguaia, Paraguai and Paranaíba in lat. 16°-l 9°S, long. 52°-55°W, known only from Sa. das Tabocas (at 700 m) in far s.-w. Goiás, Brazil and from mun. Rio Verde in adjoining Mato Grosso do Sul.—Fl. IV-VI.
Distribution:Brazil South America
| Goiás Brazil South America
| Mato Grosso do Sul Brazil South America