Monographs Details: Mimosa microcephala subsp. microcephala var. microcephala
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 microcephala Humb. & Bonpl. ex Willd.
Description:Variety Description - Leaf-formula xiv-xxii/20-35, the longer lfts 2-3.5 x 0.4-0.7 mm, obtuse; corolla minutely puberulent or subglabrous, the lobes finely prominently 3-nerved; pods ±25-45 x 4 mm, 5-9 seeded.

Distribution and Ecology - In savanna thickets and about crystalline outcrops, 70-150 m, locally plentiful along and near the Orinoco River between Sanariapo and Cerro San Borja in n.-w. T. F. Amazonas and immediately adj. Apure and Bolívar, Venezuela; adj. Vichada, Colombia.—Fl. intermittently through the year.

Discussion:

The varieties microcephala and communis are essentially identical except in venulation of the corolla-lobes, a character that bears on the relationship between M. microcephala and M. somnians, not perceived by Bentham. The var. microcephala has been collected repeatedly, and to the exclusion of var. communis, in the environs of Puerto Ayacucho, but upstream at Sanariapo and downstream on Cerro San Borja the two varieties occur in close proximity, differing, at least at Cerro San Borja, further in color of filaments, pink in var. microcephala (Wurdack & Monachino 39826, NY) and white in var. communis (Wurdack & Monachino 39842, NY, further notable for an extremely long pod with up to 16 articles). Also present on the crystalline rock-savannas of this sector of the Orinoco is M. somnians var. deminuta, and it seems possible that the venulose corolla-lobes of var. microcephala may be derived by introgressive hybridization from this source. If other populations of var. communis that are sympatric with var. microcephala have the multiovulate pod of Wurdack & Monachino 39842 they may eventually deserve taxonomic status.

Distribution:Venezuela South America| BolĂ­var Venezuela South America| Apure Venezuela South America| Colombia South America| Vichada Colombia South America|