Mimosa dichroa Barneby
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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
64. Mimosa dichroa Barneby, nom. nov. M. discolor Bentham, J. Bot. (Hooker) 4: 391. 1842, horn, illeg.—"Goyaz, Gardner", the locality particularized in Martius, Fl. bras. 15(2): 356. 1876: ". . . in collibus siccis ad Arrayas [Goiás, 13°S, 47°W. . .]."—Ho
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Synonyms
Mimosa discolor Benth.
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Description
Species Description - Unarmed, amply microphyllidious arborescent shrubs flowering when 2-4 m tall, the hor- notinous stems and foliage except for facially glabrous lfts finely puberulent with fine gray hairs to 0.1-0.25 mm mixed with minute livid or reddish granules, the firm plane, sometimes minutely ciliolate lfts bicolored, when dry brownish-olivaceous above, paler brown or subglaucescent beneath, the inflorescence a simple pseudoraceme or few-branched panicle of fl-spikes exserted 2-5 dm beyond expanded lvs. Stipules erect firm linear-attenuate involute 2-5 x 0.5-0.9 mm, subpersistent. Leaf-stalks 6-16 cm, the petiole including livid wrinkled pulvinus (1.3—)2—3 cm, near middle 0.9-1.6 mm diam., the longer interpinnal segments 11-19 mm, the ventral groove interrupted between pinna-pairs by an arched bridge sometimes produced as an incipient spicule; pinnae 5-10-jug., only a little decrescent proximally, the axis of longer ones 6-9.5 cm, the longer interfoliolar segments 2-3 (-3.5) mm; lfts of longer pinnae 20-32-jug., little graduated, the first 1-1.5 mm distant from subulate paraphyllidia, all in outline linear-oblong obtuse, the longer ones 7-11.5 x 2-2.7 mm, the subcentric costa weakly prominulous beneath, other venules immersed. Flower-spikes 2-5 per node, the axis including short peduncle 2.5-6 cm; bracts linear-lanceolate 0.7-1.7 mm, caducous; fl-buds plumply obovoid, at least thinly gray-pilosulous; flowers 4-merous 8-androus, many staminate; calyx campanulate, externally puberulent 0.7-1 mm, the deltate lobes 0.2-0.3 mm; corolla pink turbinate 2-2.5 mm, the ovate 1-nerved lobes 0.8-1.1 x 0.7-0.8 mm; filaments either pink or in age whitish, free to base, the longer ones exserted 4-7 mm; ovary gray-pilosulous; pod unknown.
Distribution and Ecology - In cerrado or cerradão at ±550-700 m, locally endemic to the Brazilian Planalto, known only from e Paranã-S. Francisco watershed between 12° and 14°30'S in centr. and e.-centr. Goiás (Arraias; Monte Alegre de Goiás; Uruaçu) and adj. Bahia (mun. Barreiras).—Fl. X-V.
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Discussion
Until the pod is discovered, the status of M. dichroa in relation to M. acutistipula will remain uncertain. The coarser foliage, the thick-textured, faintly and simply costate leaflets, the long-exserted panicle, the usually pink filaments, and the pilosulous ovary and puberulent corollas provide for the present a seemingly strong differential syndrome, but each individual difference is of small weight in itself, and will require reevaluation when the pod is known. Mimosa dichroa also resembles M. interrupta in leaf-formula, but differs in lack of prickles, no resinous exudate, and externally pilosulous flowers with more deeply campanulate calyx. Here again the fruit may eventually provide stronger contrasts. Mimosa apodocarpa and M. xavantina, also similar in gross facies, have leaflets gland-sprinkled beneath and white filaments.
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Distribution
Brazil South America| Goiás Brazil South America| Bahia Brazil South America|