Monographs Details: Mimosa uniceps 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 uniceps Barneby
Description:Species Description - Diminutive tufted unarmed subshrubs 1-1.5 dm with loosely cespitose, shallowly subterranean caudex and slender erect stems ±3-6-lvd at and above middle, the stems, lf-stks and solitary subterminal peduncles all hispid with spreading-ascending, either short and stout or longer flagelliform setae to 0.6-1.6 mm, the firm brown-olivaceous, incipiently glaucescent lfts facially glabrous except for dorsal face of proximal pair, comeous-marginate and setose-ciliate, the subglobose capitula immersed in foliage. Stipules firm lanceolate 1.5-3.5 x 0.4-0.7 mm, either glabrous or setose dorsally, setose-ciliate, persistent. Leaf-stalks erect slender (1-) 1.3-3 cm, at middle 0.3-0.5 mm diam., obscurely sulcate; pinnae 1-jug., ascending from tip of lf-stk, the gently retro-arcuate rachis 2-4(-5) cm, the longer interfoliolar segments 2-3 mm; lfts of some short lower lvs (4-)7-12-, of longer distal ones to 20- jug., decrescent near base of rachis but scarcely so distally, in sleep subvertically imbricate, the unequal first pair 1-1.5 mm distant from subulate paraphyllidia, the blades obliquely oblong, abruptly apiculate, the longer ones 5.5-7.5 x 1.6-2.2 mm, ±3.5 times as long as wide, at base shallowly cordate on proximal side, dorsally 4-nerved from pulvinule, the midrib displaced to divide blade 1:2-2.5, the inner of three posterior nerves attaining ±3/4 length of blade and expiring within the margin, the outer primary nerves much shorter, all fully immersed on upper face. Peduncles subterminal solitary erect ±25 mm; capitula (seen only past anthesis) subglobose, without filaments ±8 mm diam.; bracts oblanceolate 1.7-2 x 0.7 mm, setose dorsally and marginally; flowers 4-merous 4-androus, most proximal ones staminate; calyx paleaceous glabrous ±2.3 mm, cleft to below middle into four lacerately setose lobes; corolla 2.8-3 mm, narrowly funnelform, the cymbiform, externally sublustrous, microscopically puberulent lobes thickened but scarcely corneous; filaments not seen entire. Pods ±3-10 per capitulum, not forming a dense ball, subsessile, when well fertilized narrowly oblong obtuse ±15 x 4.5 mm and 2-seeded but often broadly elliptic and one-seeded, the densely ascending-setose replum 0.4-0.6 mm wide, the firmly papery low-convex valves at middle ±0.1 mm thick in section, a little thicker at margin, densely hispid with fine ascending setae to ± 1 mm, when ripe separating in one piece from replum and inertly dehiscent along the sutures, apparently not breaking transversely between seeds, these (1 seen) compressed-obovoid ±4 x 2.7 mm, the brown testa smooth dull.

Distribution and Ecology - In campo rupestre at 1300 m, known only from the crest of Sa. do Espinhaço 20 km s.-w. of Diamantina, near 18°25'S in centr. Minas Gerais, Brazil.—Fr. ripe in I.

Discussion:

 

Mimosa uniceps, a clearly specialized species of campo rupestre, forms dense clumps of foliage rising about 10 cm above soil-level from a branched subterranean caudex. In its dwarf stature and monocephalous stems it stands apart from all other Polycephalae except the scapose M. pumilio of Chapada dos Veadeiros in Goiás. The small pod with, when two-seeded, valves that fall from the replum in one piece is atypical of Polycephalae. The species may be related to M. hirsutissima rather than to the core of subser. Polycephalae, but has unarmed stems and conjugate pinnae that only exceptionally coincide in M. hirsutissima and then in diffuse plants with stems several times longer and much longer axillary peduncles. Fresh flowers are required to determine the form of the androecium.

Distribution:Brazil South America| Minas Gerais Brazil South America|

Narratives:Mimosa uniceps
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