Monographs Details: Mimosa involucrata Benth.
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
Description:Species Description - Unarmed humifuse shrublets with adventitiously rooting woody branches, the short, densely foliate homotinous branchlets incurved-ascending, these with lf-axes pilose with slender ascending flagelliform, proximally branched setae ±1-1.5 mm, the foliage gray concolorous, the imbricate lfts subappressed-plumulose-setose beneath, densely stellate above, continuously pallid-marginate and finely setose-ciliate, the broad hemispherical capitula solitary and short-pedunculate in distal lf-axils. Stipules erect lanceolate 2.5-5 x 0.8-1.4 mm, 3-nerved, early dry papery brownish, dorsally glabrous or early glabrate, persistent. Leaf-stalks 2-6 x 0.4-0.6 mm; pinnae 1-jug., the rachis 9-24(-28) mm, the interfoliolar segments ±1-1.5 mm; lfts (8-)9- 15(-17)-jug., scarcely graduated, the first pair ±0.5 mm distant from minute setiform paraphyllidia, the blades oblong-elliptic from semicordate base, deltately acute, the longer ones ±4.5-8 x 1.5-2 mm, all shallowly concave ventrally, nerveless above, beneath 1-2-nerved, the simple midrib moderately displaced, the posterior nerve expiring near or short of mid-blade. Peduncles 3-14 mm; capitula without filaments ± 1 cm diam., prior to anthesis conelike and at anthesis resembling the capitulum of some Asteraceae, involucrate by 3-4 graduated ranks of pallid lanceolate, dorsally puberulent, internally glabrous bracts, the fls all subvertically ascending; involucral bracts resembling stipules in texture but more densely puberulent dorsally, the outermost 2-3 mm, the inner to 12 mm long, the bracts subtending fls narrower and of thinner texture, much surpassing the associated fl, plumulose-ciliate; flowers 4-merous 4-androus; calyx hyaline, less than 1 mm, minutely toothed, externally glabrous, silky-ciliolate; corolla membranous, narrowly vase-shaped ±4.5 mm, the plane ovate 1-nerved lobes ±1.2 x 1 mm, thinly silky dorsally; filaments pink (teste Lins), free to base, exserted ±3 mm. Pod subturgidly ellipsoid 8-14 x 5-7.5 mm (l-)2—4-seeded, the valves densely comose-setose, when ripe breaking up into free-falling, individually dehiscent articles, the cavity divided by membranous interseminal septa.

Distribution and Ecology - In rocky campo and on moist stony stream-banks on and near the crest of the coastal Cordillera of extratropical Brazil in lat. 25°30'-29°S, in scattered stations from far e. Paraná (Morretes) to s.-e. Sta. Catarina and immediately adj. Rio Grande do Sul (but see discussion immediately following).—Fl. IX-IV.

Discussion:

Lins (1984) recorded the fresh filaments of this remarkable minosa as pink and the outer involucroid bracts of the capitulum whitish or yellowish when fresh, but deciduous. As she has remarked (l.c.), the capitula, which resemble superficially those of some Compositae, are indeed unique in sect. Calothamnos and the prostrate habit is matched only in M. lepidorepens.

A specimen labelled "São Paulo" (Gaudichaud 8431, BM) may in reality be part of a Sello gathering from further south. A second, Glaziou 8431 (P), said to be from Serra do Mar in far southwestern Rio de Janeiro ("haut de la Serra do Ariro [Arire].-Bel arbuste, fl. jaunes."), may be another case of spurious locality data and actually collected by Mosén or Puiggari far to the southwest of Rio (cf. Wurdack, Taxon 19: 911. 1970). At the very least these intratropical localities require modem confirmation.

Distribution:Brazil South America| Paraná Brazil South America| Rio Grande do Sul Brazil South America| Santa Catarina Brazil South America|