Monographs Details: Mimosa pratincola 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 gracilis subsp. filiformis (Benth.) Barneby, Mimosa gracilis var. invisiformis Barneby
Description:Species Description - Unarmed perennial herbs with pliantly humifuse, remotely few-branched stems to ± 1 m, these and the lf-axes puberulent with fine recurved villi to 0.2-0.4 mm, neither pilosulous, nor glandular, nor setulose, the lfts and the globose or plumply ellipsoid capitula glabrous, the capitula axillary and distally pseudoracemose. Stipules lanceolate 2-4 x 0.5-0.8 mm, indistinctly several-nerved. Leaves sessile, the lf-stk 2.5-5 cm, the longer interpinnal segments 4-7 mm, and between pinna-pairs a low-deltate scalelike spicule ±0.4 mm; pinnae 5-8-jug., subequilong, the first pair next to lf-pulvinus, the slender rachis 12-20 mm; lfts of longer pinnae 7-10-jug., the first pair 1-1.5 mm distant from subulate paraphyllidia 0.3-0.4 mm, the blades narrowly oblong or oblong-oblanceolate obtuse ±3-4 x 1 mm, plane, veinless above, beneath faintly 2-nerved from pulvinule, the midrib subcentric. Peduncles heliotropic ± 3-4 cm; capitula without filaments ±5.5 mm diam., prior to anthesis moriform; bracts linear-oblanceolate 2-2.5 mm; flowers 4-merous 4-androus, the lower ones staminate and a little smaller, all glabrous overall; calyx 0.5-0.7 mm, broadly shortly toothed; bisexual corollas ±3 mm, the ovate, apically incurved but scarcely callous lobes 1.5-1.8 mm; filaments pink, exserted 4.5 mm; ovary glabrous; fruit unknown.

Distribution and Ecology - Prostrate in brejo, the stems threading through grasses and sedges but not adventitiously rooting, known only from the type-locality, at ± 1100 m on the Tocantins slope of Sa. Geral do Paranã near 14°30'S in e.-centr. Goiás, Brazil.—Fl. II- III(-?).

Discussion:

In habit M. pratincola resembles humifuse forms of M. gracilis sensu lato but differs from all of them in essentially sessile leaves, the first pair of pinnae arising directly beyond the leaf-pulvinus. The form of M. gracilis most common in east-central Goiás is var. invisiformis, found not in brejo but in campo rupestre and dry cerrado habitats, and this differs further from M. pratincola in at least thinly aculeolate stems and in pilosulous stems and flowers. The type-population of M. pratincola was taken from saturated sandy-clay soil of brejo, where it formed extensive carpets of interlacing humifuse stems.

Distribution:Brazil South America| Goiás Brazil South America| Paraná Brazil South America|