Monographs Details: Mimosa bipennatula 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 jacobita Barneby
Description:Species Description - Slender erect unarmed shrublet ±1 m, with spindling defoliate trunk branched distally, the subvertical microphyllidious lvs crowded toward tip of young branchlets, the homotinous stems and lf-stks strigose with dorsally flattened, closely appressed smooth setae mostly 0.5-1.5 mm (but some flagellately attenuate to 3 mm), the extremely narrow and densely imbricate lfts finely pallid-marginate and setose-ciliate but otherwise glabrous, the small, plumply ovoid capitula solitary in a few distal lf-axils, immersed in foliage. Stipules erect, firm lanceolate ±3-4 x 0.8 mm, facially glabrous, setose-ciliolate, striately 5-7-nerved, persistent. Leaf-stalks including hard but scarcely swollen pulvinus 2.5-3.5 mm, near middle 0.5-0.6 mm diam.; pinnae 1-jug., erect from narrowly ascending lf-stk, the rachis 3-4 cm, the interfoliolar segments ±0.3 mm; lfts 70-85-jug., subcontiguously stacked face-to-face in narrowly ascending files, subdecrescent at each end of rachis, all narrowly linear acute, those near mid-rachis 3.5-4.5 x 0.3-0.4 mm, 10-11 times as long as wide, the blades veinless above, beneath finely centrically 1-nerved. Peduncles 4-5 mm; capitula without filaments ±3 mm diam., prior to anthesis moriform; bracts narrowly elliptic cymbiform ± 1 x 0.5 mm; flowers 4-merous 4-androus, the lower ones staminate; calyx paleaceous 0.6-0.7 mm, the lacerately decompound lobes united into a tube ±0.2 mm, externally glabrous; corolla turbinate 4-angulate 1.6 mm, the membranous tube glabrous, the cymbiform, distally subcallous lobes 0.6-0.4 mm, setulose on either side of the glabrous keel; filaments pink, obscurely monadelphous at very base, exserted ±6 mm; ovary at anthesis glabrous; ovules 4. Pods 1-few per capitulum, sessile, in profile linear-oblong, including terminal cusp ±23 x 3.5 mm, 3-4-seeded, the slender replum undulately constricted, strigose with forwardly subappressed setae 2-2.5 mm, the valves glabrous, breaking up into articles 4.5-5 mm long; ripe seeds unknown.

Distribution and Ecology - On sandstone outcrops near 600-650 m, known only from Chapada dos Guimarães (Mata Fria; Buriti) n.-e. of Cuiabá, Mato Grosso, Brazil.— Fl. XI-?

Discussion:

Mimosa bipennatula might be visualized as a decidedly fruticose yet very slender, short-leaved form of the common M. xanthocentra var. subsericea, but may be distinguished by the elegantly striate stipules, the short pinnae, and the continuously marginate leaflets. The forms of var. subsericea known to occur on Chapada dos GuimarĂ£es have, in addition, much larger leaflets. The close affinity of M. bipennatula is with M. jacobita, found in similar rupestral habitat at the western edge of the ParanĂ¡ basin in Bolivia.

Distribution:Brazil South America| Mato Grosso Brazil South America|