Monographs Details: Mimosa luciana 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.
Synonyms:Mimosa schleidenii Herter
Description:Species Description - Slender, stiffly branched unarmed microphyllidious shrub of unknown stature, the terete purplish-brown branchlets, lf-axes and peduncles thinly hispidulous with spreading-ascending setae to ± 1 mm, the firm brown-olivaceous lfts glaucescent on upper face, glabrous on both, finely continuously callous-marginate and weakly remotely setose-ciliolate, the globose capitula solitary on short peduncle in lf-axils toward end of branchlets or subterminal to axillary short-shoots, the peduncle shorter than subtending lf. Stipules erect firm, lanceolate 2-4 x 0.6-1.2 mm, mostly 3-nerved from base, glabrous facially, thinly setulose-ciliolate, persistent. Leaf-stalks including pulvinus 1-1.5 x 0.3-0.6 mm; pinnae 1-jug., the rachis 8-22 mm, the interfoliolar segments 0.3-1.1 mm; lfts of major lvs 10-18-jug., of some diminished lvs of brachyblasts (no further described) only 7-10-jug., a little decrescent at each end of rachis, the small first pair arising 0.2-0.5 mm distant from ascending subulate paraphyllidia 0.2-0.6 mm, the blades oblong from obtusely auriculate base, deltately subacute, the longer ones 2.5-4.8 x 0.7-1.5 mm, 3-3.6 times as long as wide, all nerveless above, 2-nerved beneath, the scarcely prominulous midrib and the posterior nerve subequidistant from pallid marginal nerve ±0.1 mm wide, the posterior nerve expiring beyond mid-blade. Peduncles 6-12 mm; capitula without filaments 5-6 mm diam., prior to anthesis moriform, the 4-angulate obtuse fl-buds thinly gray-puberulent; bracts 1-1.7 x 0.3-0.7 mm, 1-nerved, persistent; flowers 4-merous 4-androus, all bisexual; calyx campanulate 0.2-0.25 mm, the obscurely lobulate rim ciliolate with setulae 0.1-0.2 mm; corolla narrowly vase-shaped 2-2.3 mm, the tube thinly retrostrigulose, the ovate, weakly 1 -nerved, shallowly concave lobes a little thickened distally, puberulent externally with antrorse-spreading hairs; filaments (presumably pink) obscurely united at very base into a stemonozone at base of ovary stipe, exserted ±4 mm. Pods (not seen fully ripe) numerous in dense clusters, subsessile, in profile narrowly oblong 2-seeded or elliptic 1-seeded, including terminal cusp 9-14 x 4 mm, the replum 0.5 mm wide, shallowly constricted when two ovules mature, the valves colliculate over each seed and like the replum strigose with narrowly ascending setae ±1-1.5 mm, apparently separating into free-falling articles.
Distribution and Ecology - In unrecorded habitat, probably near or below 100 m, known only from the type-locality in s. Uruguay.—Fl. XI-II.
Mimosa luciana differs from all other Reptantes in stiffly branched stems, small short leaves, and shortly pedunculate capitula, consequently in general habit and appearance. In firm-textured, strongly marginate leaflets it resembles sympatric M. schleidenii, but the corolla is retrostrigulose only below the lobes, which are loosely antrorse-puberulent. While I have no doubt about its status as a distinct species, the affinities of M. luciana may require reassessment as more is learned about its habitat, dispersal, and possible origin through introgression between M. schleidenii and some other group of ser. Mimosa.
Distribution:Uruguay South America