Mimosa myriophylla Bong. ex Benth.
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Authors
Rupert C. Barneby
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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.
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Family
Mimosaceae
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Scientific Name
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Type
306. Mimosa myriophylla Bongard ex Bentham, J. Bot. (Hooker) 4: 384. 1841.—"Brazil, Sello, [Riedel commun.] Langsdorff.", the second expanded in Martius, Fl. bras. 15(2): 342. 1876 to: "... ad Pombal provinciae Minas Geraës (?): Riedel."—Lectotypus, Sello
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Synonyms
Mimosa pluriracemosa Burkart
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Description
Species Description - Unarmed, amply microphyllidious shrubs attaining ± 12-20 dm, the stems and lf-axes minutely but often densely puberulent and thinly strigose with appressed, proximally scaberulous setae to 0.6-1.4 mm, the small crowded thick-textured, dull brown concolorous, facially glabrous or subglabrous lfts marginally ciliolate or weakly remotely setulose-ciliolate and granular, the axis of the subspiciform, simple or few-branched multicipital inflorescence more densely strigose or hispid with subappressed or ascending-incurved, sometimes rufescent setae and exserted 2.5-5.5 dm from foliage, the ovoid-suborbicular capitula sessile or on peduncle scarcely as long as their long diameter. Stipules firm erect linear-lanceolate 3.5-6 x 0.45-0.8 mm, inperceptibly nerved, persistent. Leaf-stalks 5-12 cm, the petiole including hard obese pulvinus ±10-15 mm, of some early lvs to 25 mm, at middle 0.7-1.4 mm diam., the interpinnal segments 3-9 mm, the ventral groove subobsolete, interpinnal spicules 0; pinnae (8-11)11-24-jug., subequilong or distally decrescent, the rachis of longer ones (23-)30-53 mm, the interfoliolar segments 0.3-0.7(-0.8) mm; lfts of longer pinnae (38-)40-65-jug., subequilong except at very ends of rachis, the first pair 0.1-0.4 mm distant from subulate paraphyllidia 0.15-0.5 mm, the blades oblong-elliptic, straight or subfalcate, at apex obtuse or subobtuse apiculate, at base triangular- auriculate postically, the larger ones (1.7—)2— 3.2(-3.6) x 0.7-1.1 mm, 2.9-3.5 times as long as wide, all veinless externally except for faintly paler or discolored but not prominulous midrib, this perceptible only dorsally. Inflorescence stiffly virgate or 1-4-branched proximally, the branches when present much shorter than the central axis, narrowly ascending; capitula plumply ovoid or subglobose, without filaments 5-5.5 mm diam., prior to anthesis moriform; fl-buds ovoid, bluntly 4-angulate, gray-puberulent; bracts heteromorphic, the lowest ovate-acuminate, the upper oblanceolate, all ±1.7-2.3 x 0.4-1 mm, dorsally puberulent distally on either side of glabrous keel; flowers 4-merous 4-androus, in some capitula all staminate, in others all but the lowest bisexual; calyx paleaceous-pappiform 1.3-2.2 mm, the lobes variably decompound into slender setae; corolla 1.9-2.7 mm, that of lowest flowers turbinate, of the rest vase-shaped, the ovate-cymbiform, apically thickened lobes 0.6-2 x 0.6-0.8 mm; filaments dark red, free to base or nearly so, exserted 3.5-4.5 mm; anthers pallid, relatively very large, 0.7-0.9 mm diam.; style slenderly claviform glabrous 0.7-0.85 mm; ovary whitish-pilosulous; ovule one. Pods numerous per capitulum, sessile in spherical capitula ± 8-9 mm diam., each in profile obliquely elliptic obtuse cuspidulate 4—4.5 x 2.5 mm, 1-seeded, the replum ±0.4 mm wide, the stiffly papery valves separating when ripe both from the replum and from one another, the replum and valves alike minutely puberulent and hispid overall with straight ascending tawny setae to ± 1.5 mm; seeds (few seen) in profile narrowly obovate 2.1 x 1.4 mm, the testa fuscous dull.
Distribution and Ecology - In campo, attaining 1250 m in centr. Minas Gerais but lower s.-ward, apparently rare and scattered: Sa. do Espinhaço in centr. Minas Gerais (s.-w. of Diamantina); upland s.-w. Minas Gerais (Poços de Caldas; Camanducaia) and adj. S. Paulo; disjunct (by present evidence) in lowland deptos. Paraguarí and Misiones, Paraguay, in Misiones, Argentina, and adj. Rio Grande do Sul, Brazil; reported (Malme, 1931: 11) further from n.-e. Rio Grande do Sul (Vaccaria, Dutra 432) and from Sta. Catarina (Sello 4385) but unknown from the latter state by Burkart (1979).—Fl. I-IV(-?). Map 45.
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Discussion
Mimosa myriophylla and M. callidryas (which see for commentary) together are diffeent from all other members of the genus in the relatively immense anthers that coincide with a short stout style enclosed in or scarcely emergent from the corolla. Auguste de Saint-Hilaire first noted the short style in February 1821 (Fieldbook C2, no. 2654, P) in plants encountered on rio Mbutui near San Borja on the Brazilian side of the Uruguay river, and Burkart in the protologue of M. pluriracemosa (1947) and in description and figure of the same in his revision of Argentine Mimosa (1948) wondered about its normality. It appears to be a constant feature of M. myriophylla and M. callidryas, the flowers of which seem to be adapted to self-pollination. Burkart cannot have known that the type of M. myriophylla is likewise brachystylous, for he compared M. pluriracemosa in the first place with M. candelabrum and in the second with M. regnellii, both dolichostylous and small-anthered, and quite distinct in other features also. Mimosa pluriracemosa was thought by Burkart to differ from M. myriophylla in slightly fewer pairs of pinnae and sometimes larger leaflets, but these differences are poorly expressed in the material now available, and do not coincide with geographical dispersal. There is also some variation in length of the peduncles, the capitula in highland Minas Gerais and S. Paulo being sessile, but in lowland habitats along the lower Paraná and Uruguai rivers often shortly stalked. But stalked and almost sessile capitula are found among syntypes of M. myriophylla collected by Riedel (287. 312 respectively, NY).
The exact provenance of the two collections of M. myriophylla described by Bentham is unknown. Sello’s specimens have neither number nor locality ascribed to them, and could have been collected either in tropical or southern extratropical Brazil. The Pombal of Riedel’s label, which Bentham surmised to be in Minas Gerais, has not been identified, and no such place is mentioned in Urban’s itineraries of Lund or Riedel.
I am grateful to Dr. M. Lavin for procuring photographs of part of the type of M. pluriracemosa at LIL.
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Distribution
Brazil South America| Minas Gerais Brazil South America| Santa Catarina Brazil South America| Rio Grande do Sul Brazil South America| Argentina South America| Misiones Argentina South America| Paraguay South America| Misiones Paraguay South America|