Monographs Details: Mimosa hilariana 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
Scientific Name:Mimosa hilariana Barneby
Synonyms:Mimosa paranapiacabae Barneby
Description:Species Description - Wandlike subshrubs ±8-15 dm with simple or distally 2-3-forked, stiffly erect defoliate trunk 2-3 mm diam. and scaly with dry persistent stipules, the homotinous branchlets densely clad with small sessile, forwardly imbricate lvs, the young foliage and stems at once minutely puberulent and pilose with very slender, sinuously flagelliform setae to 1-2 mm (the setae scabrous and deflagellate in age) and armed at each node with a weak inconspicuous retrorse or incurved infrapetiolar setaculeus 0.5-1.3 mm, the subvertically imbricate lfts brown-olivaceous above, a little paler beneath, microscopically puberulent overall and weakly discontinuously setulose-ciliolate, the small, plumply ellipsoid capitula solitary in distal or subterminal lf-axils, lateral in fruit. Stipules erect, ovate or lanceolate 3-7 x 0.7-1.2 mm, striately 5-9-nerved, minutely puberulent dorsally, pectinately setose-ciliate, papery and persistent after fall of lf. Leaf-stalks reduced to a sessile, stipuliform terminal appendage, the pulvini of the one pair of pinnae contiguous to stipules; pinnae narrowly ascending, the rachis 4-15 mm, the interfoliolar segments 0.5-1.4 mm; lfts 8-12-jug., subequilong, the first pair contiguous to submembranous, subulate or setiform paraphyllidia 0.5-0.9 mm, the ventrally shallow-concave blades elliptic-oblanceolate or -obovate from deeply semicordate base, obtuse at apex, ±3-5.5 x 1.1-2 mm, 2.3-4.1 times as long as wide, finely 5-6-nerved from pulvinule, the subcentric midrib simple or distally 1 -branched, the inner anterior and posterior nerves produced well beyond mid-blade, the outer ones shorter, the venulation of upper face prominulous to tip, of lower face prominulous below mid-blade, thence immersed. Capitula (seen in fruit only) without filaments ±5 mm diam.; bracts firmly papery oblance-obovate 1.5-2.5 x 0.5-0.8 mm, striately 5-10-nerved, distally incurved and concave, pectinately ciliolate, persistent; flowers (described from marcescent fragments) 4-merous 4-androus; calyx ±0.7 mm, irregularly denticulate ±1/3 its length, the orifice minutely ciliolate; corolla turbinate 1.7-2 mm, the ovate, shallowly concave 1-nerved lobes 0.7 x 0.4-0.5 mm, gray-puberulent dorsally; filaments free at base, not seen entire. Pods 2-5 per capitulum, sessile, in profile broadly elliptic or suborbicular, broadly rounded at each end, 6-12 x 4-6.5 mm, 2-4-seeded, the replum 0.4-1 mm wide, densely hispid with antrorsely ascending flagelliform setae ±1.5 mm, cuspidulate at apex, the papery valves colliculate over each seed, hispid like the replum but with yet longer setae, when ripe separating in one piece from each other and from the replum but only tardily deciduous, long attached at very base; seeds not seen.

Distribution and Ecology - In wet campo or at margin of brejo, ±800-1000 m, known only from the valleys of rios Itararé and Jaguariaíva, along and near the S. Paulo-Paraná boundary within 24°5'-25°S, 49°20'-50'W.—Fl. probably in midsummer (XIII); fr. of preceding season persistent on defoliate stems into I, IV.

Discussion:

Mimosa hilariana, first collected by St. Hilaire in 1820, then by Dusén in 1915, and rediscovered by Hatschbach in 1973, resembles sympatric M. paranapiacabae in habit, striate stipules, sessile leaves, and number of leaflets per pinna, but is singularly distinct in these features: leaflets elliptic-oblanceolate or -obovate 2.3-4.1 times as long as wide (not linear 5.5-9 times as long as wide); leaflet-blade delicately 4-5-nerved (not nerveless) above, beneath weakly nerved only proximally (not 2-nerved the whole length); calyx denticulate and minutely ciliolate (not pappiform); and a small deflexed or incurved setaculeus at very base of each leaf-pulvinus, a feature found in no related species.

Distribution:Brazil South America| São Paulo Brazil South America| Paraná Brazil South America|

Narratives:Mimosa hilariana