Monographs Details: Mimosa dolens subsp. callosa (Benth.) 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 callosa Benth., Mimosa setipes Benth., Mimosa callosa var. microphylla Chodat & Hassl.
Description:Subspecies Description - In habit, inflorescence, flower, and fruit inseparable from M. dolens sensu lato, but differing from other subspp. by very numerous and crowded lfts, in longer pinnae 33-60(-64)-jug., the largest 4.5-12 x 1.5-4 mm; stems either glabrous or thinly setose distally; leaf-stalks either all relatively well-developed and 2-5.5 cm, or some (many) abbreviated and 1 cm or less; lfts facially glabrous to thinly setulose on upper face or puberulent beneath, and the marginal nerve either coarse (like that of subsp. rigida) and with one row of cilia, or more slender (like that of subsp. acerba) and with cilia along both back and sides.

Distribution and Ecology - In wet campo and along margin of esteros, local at ±200-350 m on and around the Paraguayan Plateau s.-ward from lat. 25°S, thence s. at lower elevations to ±28°S in n. Corrientes, Argentina, e. (discontinuously, and at greater elevation) to e.-centr. Paraná, Brazil.—Fl. X-II (-?), the fruits maturing slowly and long persistent.

Discussion:

While obviously distinct from other subspecies of M. dolens in the many pairs of relatively small leaflets, M. callosa has precisely the inflorescence and infructescence of M. dolens sensu lato. Leaflets as small and similarly veined occur in M. dolens subsp. rigida var. deterior, so that only a small extension of an already wide range in leaf-formula is required to accommodate it in M. dolens.

I feel some qualms about reducing M. setipes to unqualified synonymy of subsp. callosa, although none as to its inclusion within M. dolens, for the type (Field Museum Negative 1308—the holotype is destroyed) clearly had the characteristic fruiting structure. Its stems appear to have been a little more hispid distally than in other examples of subsp. callosa, and the leaf-stalks of median and upper (but not the lower) leaves shorter. The leaflets of typical callosa are strongly callous-marginate (like those of subsp. rigida) and uniserially ciliate, whereas those of M. setipes had more slender margin setulose-ciliolate both dorsally and laterally (like that of subsp. acerba). It may represent a distinct variety of subsp. callosa, or even a parallel independent modification arisen from subsp. acerba. Modem specimens of M. setipes, and knowledge of its distribution and ecology, are indispensable for its systematic evaluation.

Distribution:Brazil South America| Argentina South America| Paraguay South America|