Monographs Details: Mimosa centurionis 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 argillicola subsp. major Hassl., Mimosa argillicola subsp. major var. intermedia
Description:Species Description - Unarmed, pliantly humifuse perennial herb with mostly simple stems 3.5-9 dm radiating from the crown of a taproot or xylopodium, the stems with lf-stks, palmatipinnate lvs and long vertical axillary peduncles at once minutely puberulent and softly thinly pilose with fine spreading or subdeclined setae to 1-1.5 mm, the brownish-olivaceous lfts smooth glabrous above, beneath a little paler, prominently venulose and thinly appressed-pilose, setose-ciliate, the long succession of mostly solitary, rarely geminate peduncles developing coevally with the associated lf and becoming longer than it, the capitula ellipsoid. Stipules firm, ascending, lanceolate 2-9 x 1.2-1.7 mm, dorsally puberulent, setose-ciliolate, striately 5-7-nerved, persistent. Leaf-stalks ±2-3(-5) cm, at middle 0.4-0.6 mm diam., openly shallow-sulcate ventrally, the dilated rachis 1-2 mm; pinnae 2(-3)-jug., the pulvini contiguous, the distal pair a little longer than the rest, their rachis (1.6-)2.5-3.5 cm, the longer interfoliolar segments 2.3-3.3 mm; lfts of distal pinnae 10-13-jug., subdecrescent at or near each end of rachis, the first pair 1.8-2.5 mm distant from linear-attenuate paraphyllidia 0.8-2.5 mm, the blades narrowly oblong or oblong-elliptic from semicordate or obtusangulate base, abruptly apiculate, those near mid-rachis ±6-9 x 2-2.5 mm, 2.8-4.1 times as long as wide, dorsally (4-)5- nerved from pulvinule, the coarse midrib displaced to divide blade 1:2-2.5, 2-3-branched on each side beyond middle, one anterior, very narrowly intramarginal nerve produced nearly to blade apex and the inner posterior one as long, the next posterior one forming near mid-blade a continuous marginal nerve, the outermost posterior one very short. Peduncles 6-8 cm; capitula without filaments 10-15 x 5.5-8 mm, prior to anthesis moriform but finely hispidulous with emergent bracteal setae; bracts narrowly oblong, abruptly attenuate distally ±2-2.5 x 0.6 mm, beyond middle minutely puberulent dorsally, 1-nerved, ciliate with fine setulae to ±0.8 mm; flowers 4-merous 4-androus, the lowest small and staminate; calyx spathiform, consisting of a scarious setiform-decompound scale ±0.8 mm on adaxial side of corolla, lacking on side facing the bract; corolla subcylindric 2.7-2.9 mm, the ovate concave, dorsally keeled and puberulent, scarcely thickened lobes 0.6-0.8 x 0.5 mm; filaments pink, free almost to base, exserted 8-9.5 mm. Pods (not seen fully ripe) ±25x6 mm, 4-seeded, the valves only minutely setulose.

Distribution and Ecology - In rich wet campo, at elevations not recorded but perhaps ±300-350 m, known only from e.- centr. Paraguay near lat. 22°30'S, to be sought on n. bank of rio Apa and its tributaries in adj. Mato Grosso do Sul, Brazil.—Fl. XII-II(-?).

Discussion:

It is not disputed that M. centurionis is related to M. morongii, to which (under the taxonomic synonym M. argillicola) Hassler subordinated it, but it differs in so many details as to deserve specific status. Lack of aculei, coarser foliage, leaflets mostly 5 (not 3)-nerved, much longer peduncles and fatter capitula contribute to a decidedly different facies. In unarmed, procumbent stems and in spathiform calyx M. centurionis resembles also M. caaguazuensis, but differs in pinnae exactly two (not mostly three) pairs per leaf, in much smaller leaflets (to 6-9, not 11-32 mm long), in ellipsoid (not globose) capitula, and in free (not monadelphous) stamens.

In addition to Fiebrig’s collections cited in the protologue of M. argillicola subsp. major I have seen only one later collection, T. Rojas 3045 (M) from a place called San Nicolás, not found on any map available to me.

Distribution:Brazil South America| Mato Grosso do Sul Brazil South America| Paraguay South America|