Monographs Details: Mimosa guilandinae var. extensissima (Ducke) 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 extensissima Ducke
Description:Variety Description - Lianas attaining 16m but some precociously flowering as diffuse or sarmentose shrubs 3 m or less, either prickly throughout or the young stems and lf-stks unarmed, the homotinous stems and the inflorescence to the glabrous fls densely furfuraceous with sessile or minutely stalked substellate reddish scales often mixed with sordid hairs to 0.1-0.25 mm, the ample lfts when dry dark brown-olivaceous sublustrous and either glabrous or transiently puberulent above, beneath lepidote and sometimes barbellate along primary nerves; leaf-stalks 6-14 cm, the petiole 3.5-6.5 cm, the 1-2 interpinnal segments 2-5 (-6) cm; nectary near base of lf-stk mounded small-pored 0.7-1.2 x 1.5-2.5 mm; pinnae 2 3-jug., the rachis 7-27 mm; lfts of all pinnae 1-jug., falcately half-ovate or half-ovate-elliptic from broadly semicordate or broadly cuneate base, mostly short-acuminate but occasionally obtuse, the furthest ones 5-13 x 2.5-7.5 cm, all 4(-5)-nerved from pulvinule; capitula loosely 5- 15-fld, the narrowly obovoid fl-buds glabrous; flowers 4-merous; filaments either connate into a tube enclosing the ovary or free almost to base; pod (little known) attaining 9-14 x 2.2-2.7 cm, minutely reddish-lepidote overall, the articles ±8-11 mm long and 2.5-3 times as wide.

Distribution and Ecology - Forming tangled thickets in forest clearings and disturbed brush-woodland, sometimes climbing high into trees at forest edge, 80-500 m, perhaps to 800 m in the Huallaga valley in Peru, discontinuously widespread on terra firme in w. and centr. Amazonia: on affluents of río Marañón in Peru (deptos. Amazonas, S. Martín and s.-w. Loreto, lat. 4-10°S), thence e. in Brazil to sources of rios Jurúa and Purús in Acre; apparently disjunct on banks of rio Tapajós and tributary streams near lat. 5°S in Pará.—Fl. X-III. Map 4.

Discussion:

The var. extensissima differs from var. duckei in leaflets of all pinnae stabilized at one pair, in sessile scales of the indumentum, in glabrous flowers, and usually in more oblique, subfalcately half-ovate outline of the leaflets. Shape of leaflets is, however, an unreliable criterion, for the anterior margin varies from straight or shallowly concave to shallowly convex, and the apex, although most commonly short-acuminate, may be broadly obtuse (Schunke V. 8308, NY). Although described from ParĂ¡, var. extensissima has since been collected only in Peru and far western Brazil, not less than ten degrees of longitude west of the type-locality, but this gap may well be filled by future exploration.

In gross aspect var. extensissima mimics M. extensa of Atlantic southern Brazil, but differs in mounded (not dish-shaped) leaf-nectaries, peltate (not verruciform) trichomes on mostly 4(- 5)-nerved (not 2-3-nerved) hypophyllum, smaller capitula, and slightly shorter filaments.

Distribution:Peru South America| Amazonas Peru South America| Brazil South America| Acre Brazil South America|