Monographs Details: Mimosa xanthocentra subsp. tremula var. tenuis
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 tremula var. tenuis Benth., Mimosa tremula Benth.
Description:Variety Description - Stems densely foliate, the narrow green pinnae (when dry) all sharply deflexed and reversely imbricate, the stems hispid with spreading-ascending setae to 1.5-5 mm, the lfts glabrous above; leaf-stalks not over 3 mm, most reduced to pulvinus or almost so; pinnae of larger lvs 2-4.5 cm, their lfts (20-)22-42-jug., spaced to 0.8-1.4 mm apart along rachis; pod of var. tremula, the valves (so far as known) glabrous, the setae of replum to 3-3.5 mm.

Distribution and Ecology - In cerrado and dry campo, ±400-650(-?) m, of remotely bicentric dispersal: s.-w. Minas Gerais (Caldas) and adj. S. Paulo (Mogiguaçu, S. João da Boa Vista, Farinha Podre, Campos da Bocaina); upper valley of rio das Mortes in s.-e. Mato Grosso (Xavantina and vicinity).—Fl. XIV. Map 63.

Discussion:

For lack of a type I cannot be absolutely certain that I here use the epithet tenuis correctly. In Flora brasiliensis Bentham evaluated var. tenuis or, to be more exact, Sello’s plant from southern Brazil, as a forma minor tenuior of the species represented by Regnell I/92 (K! S!) and Regnell III/501* (K! S! US!), the species that he called M. tremula. The var tenuis described herein is equivalent to M. tremula sensu Bentham when deprived of its type. This variety is visually striking by virtue of crowded, retrorsely imbricate, very narrow pinnae, hispid stems, and small, ventrally glabrous leaflets, but the individual flower and pod differ not at all from those of M. xanthocentra sensu lato. It seems possible that the population of var. tenuis in the two, mutually distant districts from which samples are at hand are independently derived, for they are different in minor points: at Xavantina the cauline setae are about 1.5-2 mm long and the pairs of leaflets on longer pinnae are 32-42; in Minas Gerais and S. Paulo the setae rise to 2.5-5 mm in length while leaflet-pairs are not over 20-32. It seems geographically probable that Sello’s plant was of the latter sort. In 1830 Sello took the road from Mogi das Cruces in S. Paulo east to Itajubá in Minas Gerais (cf. Urban, 1906: 110), passing directly through the known southern range of var. tenuis.

I have refrained deliberately from neotypifying var. tenuis, for a duplicate of the type may yet be found among unnumbered Sello collections in some European herbarium.

Distribution:Brazil South America| Goiás Brazil South America| São Paulo Brazil South America| Minas Gerais Brazil South America| Mato Grosso Brazil South America|