Mimosa polyantha Benth.

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 polyantha Benth.

Type

30.Mimosa polyantha Bentham, J. Bot. (Hooker) 4: 410. 1842.—"Mexico, Andrieux n. 397.", the data expanded by Bentham, Trans. Linn. Soc. London 30:418.1875 to: "Acatlán [Puebla]." —Holotypus, a plant bearing only reduced lvs from brachyblasts, K!

Synonyms

Mimosa polyantha var. levior B.L.Rob., Mimosa ionema B.L.Rob., Mimosa polyanthoides B.L.Rob., Mimosa stipitata B.L.Rob., Mimosa setigera Britton & Rose, Mimosa brevispicata Britton

Description

Species Description - Xeromorphic, drought-deciduous shrubs attaining 1-3.5 m, with stiffly flexuous, fuscous or pallid branches either unarmed or randomly armed at or close below some nodes with a single broad-based recurved aculeus 2-9 mm (exceptionally accompanied by 1-2 infrastipular ones), at anthesis diverse in aspect due to seasonal, perhaps partly genetic variation in foliage and inflorescence: at one extreme, the small, relatively simple lvs and loose fl-spikes all fasciculate on brachyblasts lateral to annotinous stems, the lvs then sometimes hysteranthous; at the other extreme, the longer ampler lvs and axillary fl-spikes borne serially along newly expanding long-shoots (the two extremes rarely coinciding on one plant), the foliage in either case pallid green concolorous, finely puberulent or glabrate. Stipules subdimorphic, those of long-shoots linear-attenuate or setiform 2-5 mm, those of brachyblasts ovate or ligulate, often tomentulose. Leaf-formula (i—)ii— vii(-viii)/7-18(-24), the lf-stks of primary lvs 3-15 cm, of fasciculate lvs ± 1-4 cm, the rachis of longer pinnae 1—3.5(—5) cm; lfts narrowly oblong or oblong-elliptic, obtuse or commonly apiculate, the longer ones (2.2-)3-7(-9) mm, (2.2-)3- 4.2(-4.5) times as long as wide, all weakly (l-)2(- 3)-nerved from pulvinule, the simple or faintly branched midrib little or scarcely excentric, the posterior nerve(s) faint and short. Flower-spikes without filaments 4.5-5.5(-6) mm diam., the axis including short peduncle (1.5-)2-4.5(-6) cm; pedicels 0-0.3 mm; fl-buds obovoid-pyriform, glabrous or minutely puberulent; flowers 4-5-merous diplostemonous, all or most bisexual; calyx shallowly campanulate or funnel-shaped 0.4-0.7(-0.9) mm, glabrous or puberulent, the orifice either truncate or minutely denticulate; corolla turbinate-campanulate 2.6-3.1 mm, cleft nearly half-way; filaments either white or lilac, monadelphous into an obscure stemonozone, exserted 3.5-7.5 mm. Pods to 10 per spike but usually fewer, stipitate, the stipe 3-10 mm, the oblong or broad-linear body (25-)30-55(-60) x (7—)8—12 mm, (4-)5-8-seeded, cuneate at base, abruptly cuspidate at apex, the replum and papery valves usually hairless, minutely reddish-granular, but sometimes hispid with erect setae to 1-2 mm, the valves bullate over each seed, breaking up into free-falling, individually indehiscent or tardily dehiscent articles 4.5-6(-6.5) mm long.

Distribution and Ecology - In matorral, thorn-forest, and tropical deciduous forest, mostly below 1300 m, becoming weedy along roadsides and in fences, widespread in tropical Mexico from the coastal plain of centr. Sinaloa s. to Nayarit and w. Jalisco, thence e. through the Balsas Depression to Puebla and s. to centr. Oaxaca.—Fl. V-IX, sporadically later (I, II). — Chacapo, espino (Guerrero).

Discussion

The complexly variable M. polyantha perhaps represents the matrix from which evolved M. distachya. It differs from M. distachya sens. lat. most obviously in more numerous and smaller leaflets, but further from var. distachya, where sympatric on the Pacific coast, in glabrous flowers, and from both this and the more northern var. laxiflora, like it in glabrous flowers, in position of the primary cauline aculei next to, not displaced below, the nodes. Mimosa distachya var. oligacantha, however, while different in fewer leaflets and in dispersal, has similarly situated cauline prickles, and consequently distinction between M. polyantha and M. distachya at the specific level is open to challenge and needs corroboration. Plants of M. polyantha that bear their flowers on brachyblasts, accompanied by or only succeeded by relatively short leaves, differ greatly in general aspect from those that bear flowers on long-shoots, when each spike is subtended, and sometimes surpassed, by a longer primary leaf. This dual aspect and variation in indumentum of the pod account for most of the synonymy listed.

Distribution

Mexico North America| Oaxaca Mexico North America| Nayarit Mexico North America| Jalisco Mexico North America| Sinaloa Mexico North America|