Monographs Details: Mimosa xavantinae 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 apodocarpa Benth.
Description:Species Description - Shrubs and treelets 2-3.5 m, often erratically armed on ribs descending from stipules and sometimes elsewhere with few distant broad-based, erect or recurved aculei (0.5-)l-4 mm (but some branches unarmed), the smooth brown stems, lf-stks and axes of inflorescence all, or at least the lf-stks, pilosulous with fine spreading-incurved gray hairs to 0.2-0.55 mm commonly mixed with random sessile glands, the firm bicolored lfts commonly glabrous but rarely thinly puberulent facially, ciliolate, beneath charged with hemispherical or lentiform golden glands to 0.1-0.2 mm diam., the inflorescence a leafless panicle of spikes exserted 3-6 dm from expanded foliage. Stipules erect linear-lanceolate 2-4.5 x 0.3-0.7 mm, tardily deciduous. Leaf-stalks 8-17 cm, the petiole including wrinkled pulvinus 14-27 x 0.3-0.7 mm, the longer interpinnal segments 6-15 mm, the ventral groove interrupted between each pair of pinnae by a stiff tapered spicule 0.6-1.5 mm; pinnae 8-16-jug., a little decrescent proximally, the rachis of longer ones 4.5-10 cm, the longer interfoliolar segments 1.5-4 mm; lfts of longer pinnae 23-35-jug., the first pair close beyond the subulate paraphyllidia, all in outline linear-oblong obtuse apiculate, straight or a little arched forward, the longer ones (5.5-)6- 10 x 1.8-2.4 mm, the blades brownish lustrous above, beneath paler and bluntly keeled by the slightly displaced costa, otherwise externally veinless. Axis of flower-spikes 3—9(—15) cm, the fls at anthesis moderately crowded; bracts elliptic-oblanceolate less than 1 mm, caducous; fl-buds plumply ovoid; flowers 4-merous 8-androus, some staminate ones a trifle smaller than the rest; calyx membranous, shallowly campanulate-crateriform ±0.4 x 1 mm, the angulate rim scarcely lobed, ciliolate; corolla white 1.8-2 mm, the ovate acute 1-nerved lobes ±1.2 x 0.8-1 mm, dorsally thinly pilosulous and golden-glandular; ovary densely pilosulous and glandular. Pods sessile, in profile broadly linear, gently arched downward, planocompressed 6-13 x 0.9-1.3 cm, the replum 0.7-1 mm wide, the stiffly papery lustrous brown or brownish-olivaceous, delicately venulose valves ±0.1 mm thick in section, dotted overall with minute sessile reddish-livid and often some slightly larger golden glands, sometimes also residually pilosulous, when ripe separating from replum and breaking up into 9-15 articles 7—10(—11) mm long; seeds compressed-ovoid or-suborbicular ±4.6-5.3 x 3.7-4.8mm, the brown or olivaceous testa smooth but dull.

Distribution and Ecology - In cerrado, 400-600 m, apparently local on headwaters of rios Araguaia and dos Mortes in e. Mato Grosso do Norte, s. to the s. slope of Sa. do Caiapó in s.-w. Goiás, and s.-w. to upper rio Cuiabá in s.-centr. Mato Grosso do Norte and to Sa. de Maracajú in centr. Mato Grosso do Sul.—Fl. XII-IV, the fruit long persistent on withered stems. Map 10.

Discussion:

Mimosa xavantinae was collected first by Malme near Cuiaba in 1903 (nos. 3159, 3159a, S!) and referred with reservations to M. apodocarpa, manifestly its closest known relative. It has the pod of M. apodocarpa, but the larger leaflets coinciding with a shallow dish-shaped calyx appear to distinguish it satisfactorily. The differential characters of the also closely related M. interrupt a have been brought out in the key to ser. Leiocarpae.

Distribution:Brazil South America| Mato Grosso do Sul Brazil South America| Mato Grosso Brazil South America| Goiás Brazil South America|