Monographs Details: Mimosa eriorrhachis 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 albolanata Taub., Mimosa cryptothamnos Barneby, Mimosa eriostachys Harms ex Glaz.
Description:Species Description - Unarmed subshrubs from knotty xylopodium with few ample lvs forming a subradical tuft, the leafless wandlike inflorescence erect, simple or 2-3-branched, (3-)4-10 dm, bearing a long succession of well-separated, mostly sessile or subsessile subglobose capitula, the lf-axes and whole inflorescence densely silky-pilose with flagelliform setae to 2-6 mm, those of lf-stks relatively short incurved-ascending, those of inflorescence extremely long fine silky and lustrous, variably spreading and entangled, the firm lustrous lfts glabrous facially, minutely villosulous- and setulose-ciliolate. Stipules very firm, ovate-acuminate or lanceolate 6-14 x 2-6 mm, those subtending capitula deciduous before anthesis, all densely flagelliform-setose externally, glabrous castaneous within. Leaf stalks (1.3-) 1.8-3.5 dm, the petiole 15-40 x 1.2-2.3 mm, the longer interpinnal segments 7-20 mm; no interpinnal spicules; pinnae 12-25-jug., decrescent proximally but otherwise subequilong, the rachis of longer ones 3.5-7 cm, the small proximal pair of lfts contiguous to pulvinus (no paraphyllidia), the longer interfoliolar segments 1-2 mm; lfts of longer pinnae 25-40-jug., in outline linear-oblong obtuse or apiculate, the longer ones 4.5- 7.5(-8.5) x 1-1.6 mm, all veinless above, obtusely 3-nerved beneath, the costa subcentric. Capitula solitary or 2-3 per node, all sessile or some proximal ones on peduncle to 1.5 cm, all prior to anthesis conelike, without filaments 11-14 mm diam.; bracts narrowly elliptic-oblanceolate 4-6 x 0.8-1.2 mm, in texture resembling stipules, densely setose dorsally; flowers 4-merous 8-androus, the lower ones staminate and a little smaller than the rest; calyx membranous, the externally glabrous turbinate tube 0.6-1.5 mm, its orifice fringed with sometimes minutely gland-tipped setae to 2-2.5 mm; corolla 4.5-5.5 mm, its narrowly funnelform tube glabrous, the membranous ovate lobes 1.4-1.7 x 1-1.3 mm, a little thickened apically and very densely setose-barbate dorsally; filaments lilac-pink, monadelphous through 0.5-0.9 mm, exserted 11-17 mm. Pods (described from weathered specimens persistent on annotinous stem) several per capitulum, sessile, in profile ± 17-23 x 10 mm and ± 5 mm thick, shortly bluntly apiculate, the replum 2-3 mm wide, the thick-textured valves separating entire from replum, this and the valves densely appressed-setose overall, the setae less than 0.2 mm diam. at base, with silky flagelliform tip; seeds not seen.

Distribution and Ecology - In cerrado and campo limpo, 850-1200 m, very local on Sa. Geral do Paranã within a radius of ± 10 km of S. João da Aliança in s.-e. Goiás (near 17°S), Brazil.-Fl. II-IV.

Discussion:

The sibling species M. eriorrhachis and M. cryptothamnos represent collectively the culmination in a series of increasingly specialized campo life-forms leading from the distinctly shrubby habit of M. claussenii, with leaves scattered along the stems of the season, through the relatively undifferentiated M. albolanata, with leafy stems going out into a virgate pseudoraceme efoliate at anthesis (but leafy afterward), to an erect, permanently efoliate wand rising from a rosette of very large radical or subradical leaves. Closely similar in habit, M. eriorrhachis and M. cryptothamnos differ in several correlated characters, as given in the foregoing diagnosis and repeated in discussion of the next. The small vicariant ranges of the two species coincide neatly with those of Chamaecrista conferta vars. simulans and machrisiana (cf. Irwin & Barneby, Mem. New York Bot. Gard. 30: 196, 1977).

Distribution:Brazil South America| Goiás Brazil South America|