Mimosa adpressa

Title

Mimosa adpressa

Authors

Rupert C. Barneby

Scientific Name

Mimosa adpressa Hook. & Arn.

Description

376. Mimosa adpressa Hooker & Amott, Bot. Misc. 3: 202. 1833.—"Uruguay, Baird. Entre Rios [Argentina], Tweedie."—Syntypi, Baird s.n., Tweedie s.n., K!; isosyntypus, Tweedie s.n., E!

M. denhardtii L. H. Bailey, Stand. cycl. hort. 4: 2054. 1916.—Named from plants cultivated in California, of unknown provenance.—No typus found at BH in 1985.—Cultivated as M. denhardtii, K!

M. adpressa sensu Bentham, 1875: 409, t. 66 (fr); Burkart, 1948: 128, fig. 19, lam. 13; Lombardo, 1964: 58, fig. 39; Burkart, 1987: 500, fig. 223.

M. appressa (var. orthogr.) sensu Bentham, 1876: 347, t. 86.

Stiff microphyllous shrubs 4-15 dm with terete flexuous, repeatedly branched stems randomly armed on intemodes with 1-2 infrastipular and sometimes 1 infrapetiolar aculei, these straight, widely ascending 3-7(-12) mm, the stems thinly or densely strigose with retrorsely appressed, dorsally compressed, basally calcarate setae to 1-1.7 mm, the pinna-rachises and fruits forwardly strigulose, the plant otherwise glabrous or vestigially scaberulous (eglandular), the crowded subconcolorous, dull olivaceous lfts finely continuously callous-marginate, the small globose capitula all solitary and sessile or subsessile in the axils of a series of coeval lvs. Stipules firm erect, lance-attenuate or ovate-triangular 1.5-7.5 x 0.7-1.5 mm, glabrous beyond immediate base, pallidly 5-7-nerved, dry and fragile in age. Leaf-stalks reduced to pulvinus or almost so, less than 3 mm; pinnae 1-jug., the rachis of longer ones 14-32 mm, the interfoliolar segments 0.4-1 mm; lfts opposite along rachis, those of longer pinnae (15-) 16-32-jug., subdecrescent at each end of rachis, the first pair 0.5-1 mm distant from subappressed, subulate or papilliform paraphyllidia 0.1-0.5 mm, the blades linear from obtusely auriculate or subrectangular base, either obtuse-mucronulate or acute, those near mid-rachis (2.7-)3-6.5 x 0.6-12 mm, the smooth corneous marginal nerve ±0.05 mm wide, all blades shallowly concave and nerveless above, beneath pallidly 2(-3)-nerved from pulvinule, the strong simple midrib only slightly excentric, the simple (inner or only) posterior nerve produced well beyond mid-blade, the outer one, when present, short and faint. Peduncles obsolete or rarely attaining 2.5 mm; capitula without filaments 4.5-7 mm diam., prior to anthesis moriform, the obtuse fl-buds glabrous or minutely scaberulous; bracts ovate or lanceolate acute 0.4-1 mm, 1-nerved, persistent; flowers 4-merous 4-androus, some lower ones staminate; calyx membranous, shallowly campanulate 0.1-0.25 mm, the rim obliquely truncate or denticulate, glabrous; corolla subtubular or narrowly vase-shaped 2.5-3.2 mm, obtusely 4-angulate, the erect ovate concave lobes 0.5-0.8 mm, scarcely thickened; filaments pink, free, exserted 3-5 mm. Pods usually several per capitulum, sessile, in profile undulately linear 13-28 x 4-5.5 mm, 2-5(-6)-seeded, the shallowly constricted replum 0.4-0.5 mm diam., the stiffly papery valves low-colliculate over each seed, like the replum strigose with strictly appressed, basally dilated, pallid-stramineous setae to ± 1 mm, the ripe valves breaking up into free-falling, tardily dehiscent articles 3.5-7(-9) mm long; ripe seeds not seen.

Forming prickly thickets in open places along and near river- and stream-banks, scattered along rio Uruguay and immediate affluents, in Argentina s.-ward from 27°S in Corrientes and Entre Ríos, thence e. into adj. Uruguay and to be expected in adj. Rio Grande do Sul, Brazil, thence along the shore of río de la Plata as far as Maldonado.—Fl. profusely X-II, sporadically through the year .—Rama negra.

The exemplary descriptions, figures and commentary on M. adpressa given by Burkart (1948, 1987, ll.cc.) are definitive. The identity of M. denhardtii could not be confirmed from isotypic material, but seems certain from Bailey’s description and from the fact that M. adpressa has been long known in cultivation in California.