Mimosa strigillosa Torr. & A.Gray
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Authors
Rupert C. Barneby
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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.
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Family
Mimosaceae
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Scientific Name
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Type
275. Mimosa strigillosa Torrey & Gray, Fl. N. Amer. 1: 399. 1840.—"Tampa Bay, also in East Florida, Dr. Leavenworth! Banks of the Mississippi, Louisiana, Dr. Carpenter! Dr. Hale! Arkansas, Dr. Leavenworth! Texas, Drummond (2nd Coll. 157, 158, 159)!"—Lecto
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Synonyms
Mimosa dolichocephala Harms, Mimosa sabulicola Hassl., Mimosa strigillosa Torr. & A.Gray, Mimosa dolichocephala var. sabulicola (Chodat & Hassl.) Hassl.
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Description
Species Description - Unarmed or weakly armed herbs from an eventually stout woody taproot, the simple or occasionally branched, bluntly bifacial stems pliantly humifuse and (especially in wet places) adventitiously rooting from nodes, sometimes covered with sediment and appearing stoloniform, precociously flowering when quite short but potentially attaining 1 (—1.5) m, the aculei when present infrapetiolar and serially scattered along the narrow edges of internodes, rarely also at base of pinnae, either straight or recurved, stramineous or pallid 0.4-1.8 mm, the stems, lf-axes and subvertically erect peduncles either strigose or less commonly hispid with forwardly appressed or sometimes widely ascending, tapering or flagelliform setae to 1-4.5 mm, the sensitive foliage olivaceous subconcolorous, the lfts glabrous facially or rarely puberulent beneath, often weakly or minutely setulose-ciliolate, the ellipsoid or short-cylindric capitula single in a long succession of lf-axils and varying from a little shorter to much longer than the associate lf. Stipules erect or subrecurved, ovate or semicircular from semiamplexicaul, sometimes shallowly cordate base, 1.5-4.5(-5) x 1.5-3.5(-4.5) mm, ±1-1.5 times as long as wide, the stiffly papery brown, glabrous or rarely minutely puberulent blades striately 10-17-nerved from base, persistent. Leaf-stalks when fully expanded (2.5-)4-14(-24) cm, the petiole (1-) 1.5-7(-19) cm, at middle 0.5-0.8(-l.l) mm diam., the longer interpinnal segments (3-)4-16(-24) mm, the narrow ventral groove interrupted between pinna-pairs by a setose bridge but spicules 0; pinnae (3-)4-6(-7)- jug., commonly subequilong, the rachis (10—) 12— 32(-45) mm, the interfoliolar segments 0.5-2 mm; lfts of longer pinnae 1l-18(-21)-jug., decrescent at each end of rachis, the first pair 0.5-2 mm distant from pulvinus (paraphyllidia 0 or reduced to a minute papilla), the blades linear from obtusangulate base, acute or apiculate at apex, straight or a little arched forward, those near mid-rachis (3.3-)4-8.5(-9) x 0.7-1.5 mm, 4-6(-8) times as long as wide, all veinless or almost so above, beneath slenderly but sharply 4-5(-7)-nerved from pulvinule, the midrib displaced to divide blade ±1:2, the single anterior, narrowly intramarginal nerve and the inner posterior one produced almost to blade apex, the anterior like the midrib weakly 1-2-branched distally, the l-2(-4) outer posterior ones much shorter. Peduncles (2-)4-16(-30) cm; capitula without filaments (8-)9-25 x (4.5-)5-8 mm, 1.5- 2.4(-3) times as long as wide, prior to anthesis moriform, the bract-tips scarcely emergent between the obovoid, densely gray-strigulose fl-bluds; receptacle setose; bracts linear-oblanceolate 1-2.4 x 0.2-0.45 mm, 1- or proximally 3- nerved, minutely ciliolate distally; flowers 4(-5)- merous diplostemonous, all but a few of the lowest bisexual; calyx submembranous, shallowly campanulate 0.3-0.45(-0.6) mm, the truncate or obscurely lobulate rim usually minutely ciliolate, sometimes glabrous; corolla 2-3.4(-4.2) mm, varying from narrowly turbinate to narrowly funnelform, the ovate, shallowly concave lobes 0.7-1.2x 0.6-0.9(-l)mm, 1-nerved, but often a little thickened intramarginally and appearing 3- nerved, externally strigulose with forwardly appressed setulae to 0.1-0.25 mm; filaments pink-lilac, monadelphous around the ovary through (0.5-)0.7-2 mm, exserted (4-)5-7.5 mm. Pods ±3-12 per capitulum ascending, obscurely stipitate, the stipe 0.5-1.5 mm, the body in profile oblong or oblong-obovate (8-) 10-17 x (4.5-)5-8 mm, 2-4(-5)-seeded or some obovate 1-seeded, obliquely truncate at apex and cuspidate at upper comer, the straight or shallowly (where ovules abort more deeply) constricted replum 0.3-0.45 mm wide, the papery stramineous or finally fuscous valves low-bullate over each seed, like the replum hispid with ascending or strigose with forwardly subappressed pallid setae ± 1-2.5 mm, the vesture not fully concealing the exocarp, the cavity with delicate membranous interseminal septa 0.3-0.5 mm wide, the articles at middle of 3-5-seeded pods ±3-5 mm long, those of 1-seeded pods and those at ends of other pods longer, all free-falling indehiscent; seeds plumply oblong-obovoid ±4-5 x 2.7-3.7 mm, the smooth testa fuscous-olivaceous dull or sublustrous.
Distribution and Ecology - On stream banks, along ditches, in seasonally wet or permanently swampy meadows, and less often in drier, gravelly or sandy places, on shingle river-banks and in savanna-brushland, flourishing either in full sun or partial shade, near sea- level to 300 m, in Argentina attaining 450 m, of wide bicentric dispersal in warm-temperate North and South America: s.-e. United States, from s. Georgia to s. Florida, w. around the Gulf lowlands to Tamaulipas, Mexico, n. in the States to s. Arkansas (Isely, 1973, map 32); basins of ríos Paraguai and Paraná from near 22°30'S in Paraguay to 32°30'S in Entre Ríos, Argentina and adj. Uruguay, w. in Argentina across Formosa and Chaco to long. 65°W in Tucuman.—Fl. in n. hemisphere IV-X(-XI), in s. hemisphere IX-III. Map 38.
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Discussion
Mimosa strigillosa is notable among close kindred for pliantly humifuse stems radiating from a taproot and for broad veiny stipules. The plants vary greatly in size of parts, in wet rich lowlands becoming long-leaved, long-pedunculate, and freely rooting from stem-nodes, and under drier regimens small-leaved, short-pedunculate, and seldom producing adventitious roots. In both hemispheres occasional populations have hispid rather than strigose-setose leaf-stalks and peduncles, and very rarely, as in the type of M. dolichocephala, minutely puberulent leaflets. In South America the corolla-lobes are densely strigulose externally, in North America only minutely so. Like Burkart (1948) and Isely (1971b, 1973) I perceive no significant racial division in M. strigillosa and, having studied all the relevant types, fully endorse the synonymy proposed by Burkart.
Burkart (1948) has suggested that the North American range of M. strigillosa may be secondary and the species autochthonous only in South America, home of its nearer relatives. Disjunctions of similar pattern and magnitude are exemplified by Rhynchosia senna and Rh. diversifolia (Grear, 1978) and by Chamaecrista calycioides (Irwin & Barneby, 1982). I know of no evidence that M. strigillosa is other than native in Florida, Texas or Tamaulipas.
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Distribution
Argentina South America| Chaco Argentina South America| United States of America North America| Arkansas United States of America North America| Florida United States of America North America| Georgia United States of America North America| Mexico North America| Tamaulipas Mexico North America| Uruguay South America|