Monographs Details: Mimosa gymnas 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.
Synonyms:Mimosa monticola Dusén
Description:Species Description - Stiffly diffuse, trailing or pendulous, distantly foliate subshrubs 5-9(-?) dm, glabrous except for rare minute setulae subtending some lft-pulvinules and in some plants a few retrorse, basifixed setae on peduncles, unarmed except (in some plants only) for rare decurved intemodal aculei 0.5-1 mm, the subterete stems purplish-livid, branched distally, the plane, rather thick-textured lfts when dry brown-olivaceous subconcolorous, eciliate, the globose or plumply ovoid capitula solitary or rarely geminate either in primary lf-axils only or partly on short branchlets lateral to primary stem. Stipules erect or decurved, triangular or lanceolate 1.5—4.5 x 0.8-1.8 mm, l-3(-4)-nerved dorsally, persistent. Leaf-stalks 1-5 cm, at middle 0.25-0.55 mm diam.; pinnae 1-jug., the rachis 18-55 mm, rounded dorsally, sharp-edged laterally, the interfoliolar segments 1.2-3 mm; lfts 10-18(-20)- jug., subdecrescent distally, the small first pair (1.2-) 1.5-3.3 mm distant from deflected subulate paraphyllidia 0.3-0.8 mm, the blades narrowly oblong-oblanceolate from obliquely obtusangulate base, obtuse at apex, those near and above mid-rachis (6—)7—15(—17) x (1.5—)1.8— 3.5(-^) mm, 3.3-4.2 times as long as wide, all veinless above, beneath slenderly 3-5-nerved from pulvinule, the simple or faintly branched midrib centric beyond mid-blade, the inner posterior nerve produced almost to blade apex, the outer ones very short. Peduncles (1.5-)2.5-5 cm; capitula without filaments (4.5-)5-6 mm diam., prior to anthesis moriform, the fl-buds bluntly 4-keeled; bracts oblanceolate or elliptic-oblanceolate 0.45-1 mm, persistent; flowers 4-merous 4-androus glabrous; calyx campanulate 0.2-0.4 mm, the orifice undulately truncate or obscurely lobulate; corolla narrowly vase-shaped 2-2.7 mm, the cymbiform, apically thickened, dorsally carinate, internally reddish lobes 0.7-1 x 0.4-0.6 mm; filaments bright lilac-pink, monadelphous through 0.4-1 mm, exserted 4-6 mm; ovary at anthesis glabrous. Pods solitary or few per capitulum, in profile linear-oblong contracted at base into a stipe ±1.5 mm, the body ±25 x 5 mm and 4-seeded, the shallowly constricted replum ±0.4 mm wide, the smooth glabrous valves low-colliculate over each seed, breaking up when ripe into free-falling articles 5-5.5 mm long; ripe seeds not seen.
Distribution and Ecology - In campo rupestre, about rock outcrops or pendulous from sandstone cliffs, or on rocky stream banks in climax rain-forest, ±700-1100 m, scattered along the w. slopes of Sas. Paraná-Piacaba and do Mar in Paraná (municípios Arapoti, Jaguariaiva, Ponta Grossa, Palmeira, Balsa Nova) and immediately adj. S. Paulo (Itararé), in lat. 24°-26°S, to be sought in adj. n.-e. Sta. Catarina.—FL. X-II.
Mimosa gymnas, so named for the hairless stems and leaflet margins, is akin to the more northern M. monticola, but a coarser plant, glabrous except for a few retrorse setae on peduncles alone, with longer leaf-stalks and larger leaflets (see key for measurements). It differs from M. glabra, which is known at present only from Rio Grande do Sul, in weak or suppressed armament, leaves larger in all parts with leaflets of longer pinnae 10-18 (not 8-10)-jugate and not nerve-marginate, and most decisively in the conventionally articulate fruit. Mimosa sparsa is obviously different in leaf-stalks only 2-4 mm and pinnae less than 1 cm long.
Distribution:Brazil South America
| Santa Catarina Brazil South America
| São Paulo Brazil South America