Monographs Details: Mimosa xanthocentra subsp. subsericea var. longepetiolata
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 longepetiolata Malme
Description:Variety Description - Described as a shrub attaining 2-4 m, appressed-setose, the lfts olivaceous, puberulent on both faces and also thinly appressed-setose dorsally; lf-stks 2-6.5 cm; rachis of pinnae (5.5-)7- 14 cm; lfts of longer pinnae typically 35-43-jug. and to 10-19 x 1.5-2.5 mm, sometimes twice as many (75-83-jug.) and only half as large (to 7.5-8.5 x 0.6-0.7 mm).

Distribution and Ecology - In disturbed woodland (? cerradão) near 700 m, known only from Chapada dos Guimaraes n.-e. of Cuyabá, Mato Grosso, Brazil.—Fl. IV- VII(-?).

Discussion:

This is an ambiguous mimosa, resembling var. xanthocentra in every respect except that it is unarmed. Malme described it as shrubby and attaining a height of two to four meters, a stature that is quite unusual in M. xanthocentra, but I can find no difference in indumentum, flower-structure, or pod. In addition to the type-collection, in which pinnae of larger leaves bear about forty pairs of leaflets to 10-19 mm long, Malme secured also on the Chapada a similarly long-petiolate plant (Malme II/3347, S) with twice as many leaflets about half as large, but seemingly not otherwise different. Furthermore, he encountered in the same vicinity plants (Malme III 3327a, G, S; Malme s.n., 2.VI. and 6.VI.1930, S) with aculeate stems that cannot be distinguished technically from some populations of extra-Brazilian var. xanthocentra. These plants exhibit in a suggestive way a variation in leaflets parallel to that just described for unarmed var. longepetiolata, one (6.VI) having about 40 pairs of large leaflets, the other to 105 pairs about half as long. It may be that var. longepetiolata is no more than a tall unarmed minor variant of var. xanthocentra, but the situation requires closer observation in the field. In any event I feel confident that M. longepetiolata is properly to be contained in the broad concept of M. xanthocentra.

Distribution:Brazil South America| Mato Grosso Brazil South America|