Monographs Details: Mimosa auriberbis 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 setosissima Taub.
Description:Species Description - Erect shrub ± 1 m with leafless sticklike old stems to ±6 mm diam. and short homotinous branchlets bearing few large lvs crowded around a short pseudoraceme of globose capitula, at once minutely villosulous and, except for faces of very numerous small crowded lfts, densely pilose throughout with loosely ascending, finely tapering lutescent setae ±3-5 mm, the inflorescence golden-barbate, nowhere glandular. Stipules lance-acuminate 5-10 x 1.5-2 mm, the firm caducous blades densely setose dorsally, glabrous chocolate-brown within. Leaf-stalks 9-20 cm, the petiole including obese hard pulvinus 5-7 x 11.8 mm, the longer interpinnal segments 8-12 mm, the ventral groove bridged between pinna-pairs but spicules 0; pinnae 13-22-jug., strongly decrescent proximally, less so distally, the rachis of longer ones 3.5-5.5 cm, the longer interfoliolar segments 0.6-1 mm; lfts of longer pinnae 35-50- jug., the first pair next to pulvinus (paraphyllidia 0), the blades narrowly oblong obtuse, the longer ones 3.5-5.5 x 0.8-1.2 mm, all faintly 3-4-nerved from pulvinule, finely setose-ciliate. Peduncles ±4 cm, most of them subtended at early anthesis by a nascent lf, the pods probably axillary and immersed in hysteranthous foliage; capitula without filaments ±13 mm diam., prior to anthesis densely golden-setose overall; bracts narrowly elliptic ±6x1 mm, hispid on back and margins with setae to 3 mm; flowers 4-merous 8-androus, the lowest ones staminate; calyx 0.7 mm, the glabrous tube concealed by a ring of bristles arising from rudimentary pedicel, the truncate rim densely ciliate with setae ±2 mm; corolla ±6 mm, the narrowly funnelform tube glabrous, the ovate, distally callous and incurved lobes ±1.5 mm, on back proximally setulose and distally setose; filaments pink, monadelphous through 1-1.3 mm, exserted ±9 mm; ovary pubescent; pod unknown.

Distribution and Ecology - In cerrado on dry hillsides near or above 700 m, known only from the type-collection from the headwaters of rio S. Bartolomeu in Distrito Federal, Brazil.—Fl. IX-X(-?).

Discussion:

I describe M. auriberbis with trepidation, being ignorant of the fruit, and in perplexity about its genuine affinities in ser. Pachycarpae; but as I am unable to refer the type to any known species, I presume to call it to the attention of botanists in the Federal District, in the hope that more can be learned about its morphology and dispersal. In some respects it recalls the micro-phyllidious forms of M. claussenii, but has leaves scarcely half as long. In detail of the flower, it seems close to sympatric M. rava, which see for comment on differences. In the diagnosis I have compared it with M. setosissima, superficially similar in leaves crowded at the end of the branches and in number and size of pinnae and leaflets; but M. auriberbis is, so far as known, a much smaller shrub with bark not exfoliating from year-old branches.

The type-collection of M. auriberbis had been distributed to the herbaria listed above before I commenced my study of the genus. The isotypes should be found there among unidentified Mimosae.

Distribution:Brazil South America| Distrito Federal Brazil South America|