Monographs Details: Mimosa maguirei 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 maguirei Barneby
Description:Species Description - Unarmed, openly few-branched, sparsely but amply leafy subshrubs and shrubs attaining 1.55 m, appearing glabrous below the yellowish-setulose capitula and the sometimes remotely hispidulous inflorescence-axes, but the pinna-pulvini densely appressed-setulose and the pinna-rachises minutely puberulent, the lustrous thick-textured lfts sometimes remotely randomly ciliolate with plain or gland-tipped setulae, the smooth terete purplish or blackish-livid homotinous stems often glaucescent in age, the inflorescence a loose pseudoraceme or panicle of pseudoracemes rising ±3-5 dm above foliage. Stipules at base of petioles, even on young flowering stems, either prematurely caducous or perhaps obsolete, those subtending peduncles lanceolate 4-6 mm, glabrous dorsally, setose-ciliate, also precociously deciduous. Leaf-stalks of primary cauline lvs (some diminished distal lvs no further described) 10-28 cm, the pulvinus early separated from stem by a deeply engraved sulcus, the subterete petiole 4.5-12 cm, at middle 1.52 mm diam., the longer interpinnal segments 2-5.5 mm; between each pinna-pair a (sometimes deciduous) spicule 0.7-1.5 mm; pinnae (3-)4-11-jug., a little accrescent distally, the rachis of longer ones 5-10 cm, the interfoliolar segments l-2(-2.5) mm; lfts of longer pinnae 40-65-jug., the first pair 1.5-3 mm distant from subulate paraphyllidia, all in outline narrowly oblong obtuse or subapiculate, longer ones 4-9 x 1.5-2.7 mm, all veinless above, weakly 3-nerved beneath, the centric midrib weakly 1-2-pinnate beyond middle. Peduncles solitary or commonly 2-3 per node, 1.5-4 cm; capitula squatly ellipsoid or globose, prior to anthesis conelike, without filaments 11-12 mm diam.; bracts spatulate-oblanceolate 3.6-4.2 x 0.8-1.2 mm, yellowish-setulose-ciliate from near middle upward, toward apex thinly setulose and glandular dorsally; flowers 4-merous 8-androus, the lowest staminate but scarcely shorter than the rest; calyx-tube shallowly campanulate glabrous 0.3-0.5 mm, the cilia of its crenulate rim to ±1-1.3 mm; corolla funnelform 3.7-5 mm, the tube glabrous, the ovate acute or obtuse membranous 1-nerved lobes 1.4-1.8 mm, neither callous nor much concave distally, dorsally thinly setulose or capitate-glandular, rarely glabrous; filaments pink, shortly monadelphous below the glabrous ovary, exserted 10-12 mm. Pods 1-3 per capitulum, sessile, in profile 20-40 x 7.5-9.5 mm, ±6-9-seeded, at obtuse apex abmptly cuspidate by thick style-base 1.5-5 mm, the replum ±1.5 mm wide, the stiffly papery nigrescent valves ±0.5 mm thick in section, externally either quite glabrous or thinly capitate-glandular (but not setose), internally rufous-furfuraceous, low-corrugate over the transverse seeds, falling from replum entire; seeds ±4-4.7 x 3-3.3 mm, the testa atro-castaneous smooth.

Distribution and Ecology - On sandstone terraces, rock-piles and outcrops, 1150-1300 m, localized on and near the crest of Sa. do Espinhaço in mun. Diamantina (near 18°15'S) and on Sa. do Cipó in mun. Jaboticatubas and Sta. Ana do Riacho (near 19°20'S) in centr. Minas Gerais, Brazil.—Fl. VIII-X, fr. XI-II.

Discussion:

Mimosa maguirei is readily distinguished from other Pachycarpae of Sa. do Espinhaço by stature, smooth livid, ultimately glaucescent stems, relatively few and distant multifoliolate pinnae, and virgate efoliate pseudoracemes far exserted above the leaves. The populations near Diamantina (at Biribiri and west and northwest of the city) appear to have slightly more numerous pairs of pinnae than those of Sa. do Cipo, but I can find no convincing evidence of racial differentiation.

What appears to be historically the first collection of M. maguirei is Glaziou 19127 (C! P! K!), in Glaziou’s Liste (1906: 183) miscited 29127 and misidentified as M. vernicosa.

On Sa. do Cipó M. maguirei is sometimes parasitized by Pilostyles (A. P. Duarte 5692, RB).

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

Narratives:Mimosa maguirei