Monographs Details: Mimosa xanthocentra subsp. subsericea var. subsericea
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 subsericea Benth., Mimosa xanthocentra var. subsericea (Benth.) Barneby, Mimosa stipularis Benth., Mimosa subsericea var. strigosa Chodat & Hassl., Mimosa subsericea var. hirsuto-strigosa Chodat & Hassl., Mimosa subsericea var. oblonga Chodat & Hassl., Mimosa loeseneriana Glaz., Mimosa subsericea Benth., Mimosa stipularis Benth.
Description:Variety Description - Indumentum of foliage variable in length and density, the lfts either green or silvery-pilose dorsally; pinna-rachis of lvs near mid-stem commonly 6—12(—14) cm, or when drought-stressed only 4-6 cm, the interfoliolar segments 0.8-4 mm, varying with width of lfts; lfts mostly at least 35-jug., if fewer at least 1.5 mm wide.

Distribution and Ecology - In cerrado and young capoeira, commonly on red sandy soils, on the Brazilian Planalto mostly at 500-1200 m but lower s.- and w.-ward, common and variable from centr. Goiás s. to interior Sta. Catarina, e. to Sa. do Cabral in centr. Minas Gerais, w. to s.-e. Bolivia, centr. Paraguay, and the lower Paraná valley in Corrientes, Argentina; adventive in Guárico, Venezuela.—Fl. IX-IV (-V), sporadically during the dry months. Map 62.

Discussion:

Two mutually independent modes of variation contribute to the more conspicuous variation within what is here defined as var. subsericea: quality of pubescence, and width of leaflets, the latter closely related to distance between successive pairs but not to their number nor, consequently, to length of pinnae. Nomenclaturally typical subsericea has narrow crowded leaflets silvery-silky beneath, whereas M. stipularis is based on a variant in which stipules broader than customary (but not unique) in M. xanthocentra sensu lato coincide with broader, more distant, but equally pilose-silky leaflets. Bentham early suggested that M. stipularis might represent no more than an extreme form of M. subsericea, and his suspicion is confirmed by the number of intermediate forms now extant in collections. Moreover, there are parallel series of thinly strigose green plants with broader and narrower leaflets which, if M. stipularis is recognized at any level, command the same attention. It is worth noting, however, that no one variant of var. subsericea occurs universally through the variety’s range and some variants appear, on present evidence, to be relatively localized—for example, plants truly equivalent in all respects to M. stipularis are known only from southern and eastern Mato Grosso—the overall picture being one of genetic drift and incipient differentiation related to dispersal.

Of the variants described by Chodat & Hassler only var. strigosa is anything out of the ordinary in var. subsericea; it has relatively few and broad leaflets which simulate those of sympatric M. polycarpa var. spegazzinii. I suspect that var. strigosa and its aculeate analogue var. strigoso-aculeata, herein referred to var. mansii, are hybrid derivatives from a cross between some unarmed form of M. xanthocentra and armed M. polycarpa spegazzinii. The type of each variety, however, has the ellipsoid capitula and pilosulous flowers of M. xanthocentra sensu lato.

Distribution:Brazil South America| Santa Catarina Brazil South America| Goiás Brazil South America| Minas Gerais Brazil South America| Bolivia South America| Paraguay South America| Argentina South America| Corrientes Argentina South America| Venezuela South America| Guárico Venezuela South America|