Monographs Details: Mimosa gracilis Benth. subsp. gracilis
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 gracilis Benth.
Description:Subspecies Description - Stems either pliantly humifuse and then potentially much elongating, or relatively short and stiff, then either prostrate or assurgent or densely tufted, never aculeolate; pubescence of subsp. capillipes; leaf-formula ii-x(-xiv)/2-9(-10), the rachis of longer pinnae 2-8 mm; flower and pod of var. capillipes, the pod either glabrous or densely villosulous, but never aculeolate.

Discussion:

This subspecies differs from both the foregoing and the following by abbreviated pinnae and consequently by leaves of proportionately long narrow outline. The var. gracilis differs sometimes from var. capillipes by length of pinnae alone, but often also by more numerous as well as shorter pinnae. In var. brevissima leaf-reduction is carried a step further, the longer pinnae being yet shorter than those of var. gracilis and commonly also fewer by at least one or two pairs. Length of pinna-rachis, number of pinnae, number of leaflets, each varies through a continuum between the average robust var. capillipes and the highly reduced var. brevissima, but the curves of variation are poorly correlated with each other. Ambiguous specimens link the three varieties, but are fewest when the arbitrarily chosen measurement of longer pinnae is accepted as the deciding factor. While var. brevissima intergrades with var. gracilis on the one hand, it is also very closely akin to, perhaps the precursor of, the yet more reduced or ultimately ephedroid, essentially efoliate M. paucifolia, M. piptostegia and M. phyllodinea.