Monographs Details: Mimosa prionopus 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
Scientific Name:Mimosa prionopus Barneby
Synonyms:Mimosa pseudocallosa Burkart
Description:Species Description - Subshrub with decumbent, nearly simple, distally quadrangular, sparsely but coarsely foliate, almost simple stems ±3(-"15") dm and thinly strigose with reflexed terete tapering setae up to 1-2 mm, the stout, dorsiventrally compressed lf-stks and bifacial peduncles densely retro-ciliate, the stiff lustrous, olivaceous or subpruinose, plane lfts callous-marginate and antrorsely setose-ciliate, the dense globose capitula of glabrous fls arising from distal lf-axils. Stipules appressed, obtusely deltate 2-2.5 x 2.5-3 mm, thick-textured, fuscous, obscurely 5-nerved, tardily deciduous. Leaf-stalks including discolored pulvinus ±2.5-5 cm, in dorsoventral view 1.2-1.5 mm wide, facially smooth but bisulcate lengthwise, the straight retrorse cilia of margin several-seriate and some basally confluent, all obliquely basifixed, distally lutescent, the terminal appendage beyond the one pair of pinnae resembling a stipule in form, texture and fuscous color; pinna-rachises 4.5-7.5 cm, their pulvinus antrorsely setulose, the longer interfoliolar segments 3-3.5 mm, glabrous except for one small antrorse seta behind each lft-pulvinule; lfts 15-19-jug., decrescent toward each end of rachis, the first pair arising ± 1.5-2.5 mm distant from a pair of ovate paraphyllidia ±1-1.3 mm that resemble stipules in form, texture and fuscous color, the blades narrowly oblong or lance-oblong from shallowly semicordate base, abruptly acuminulate, those near mid-rachis 12-17 x 3.5-5 mm, ±3.5 times as long as wide, all 3-4-nerved from pulvinule, the strong midrib forwardly displaced at base of blade becoming subcentric distally, the inner posterior primary nerve narrowly ascending to or a little beyond mid-blade, the outer ones progressively shorter, the midrib giving rise, on anterior side at and beyond middle, to 3-5 widely ascending secondary venules faintly brochidodrome immediately within the pallid corneous margin. Peduncles solitary 3-3.5 cm; capitula without filaments 8-9 mm diam., prior to anthesis moriform, the densely crowded fls subglutinously varnished, dull pink-purple; bracts linear-oblanceolate ± 1.7 x 0.3 mm; flowers sessile, 4-merous 4-androus; calyx paleaceous pallid, narrowly campanulate 1.6 x 1.2 mm, the 4 lobes fimbriately decompound at apex; corolla turbinate-campanulate 1.7 x 1.2 mm, the ascending cymbiform lobes 1.3 x 0.7 mm; filaments ±6.5 mm, pink, united at base through almost 1 mm; fertile ovary and style not seen. Pod unknown.

Distribution and Ecology - In montane campo at 1200 m, known only from the type-locality, near 25°20'S in the coast range of e. Paraná, Brazil.—Fl. III-IV(-?).

Discussion:

Mimosa prionopus is distinguished by this strong syndrome of characters: bluntly four-angled stems thinly retrostrigose with basifixed (basally ecalcarate) setae; incrassate stipules and paraphyllidia; broad, dorsiventrally compressed petioles densely retrociliate along each margin; pallid-marginate and antrorsely setose leaflets of thick texture (recalling those of M. dolens subsp. rigida); glabrous flowers; and paleaceous calyx. In the stipules and paraphyllidia it resembles M. pseudocallosa, but this is a smaller, more slender plant with terete stems and a simply lobed membranous calyx. The petiole of M. pseudocallosa is somewhat laterally dilated distally, but lacks the dense fringe of stiffly deflexed, pluriseriate setae which has suggested the epithet prionopus (Gr. prion, saw + pous, foot or foot-stalk). The paleaceous calyx with dissected lobes is unique in subser. Sparsae, most of which, furthermore, have stems either armed, or terete, or both.

The collector described the stems as reaching meters in length, but they are scarcely 3 dm in the type-specimen.

Distribution:Brazil South America| ParanĂ¡ Brazil South America|

Narratives:Mimosa prionopus