Mimosa polycarpa

Title

Mimosa polycarpa

Authors

Rupert C. Barneby

Scientific Name

Mimosa polycarpa Kunth

Description

310. Mimosa polycarpa Kunth, Mimoses 8. 1819.—Typus infra sub var. polycarpa indicatur.

Subshrubs and bushy shrubs attaining 7-20 dm, often resembling M. xanthocentra in habit and foliage and like subsp. xanthocentra armed at all or most nodes with infrastipular broad-based stramineous aculei (l-)2-7(-8) mm, the virgate or paniculately branched stems, lf-stks and peduncles either hispid-pilose or subappressed-strigose with fine tapering setae to (0.6-) 1-2.5 mm mixed with minute puberulence, the olivaceous subconcolorous lfts either glabrous or minutely puberulent above, beneath thinly appressed-setose and sometimes also puberulent, discontinuously or subcontinuously setose-ciliate, the globose or plumply ellipsoid capitula mostly 2-3-nate, rarely solitary in the axil of contemporary lvs, the immature ones sometimes forming a hysteranthously foliate pseudoraceme. Stipules firmly chartaceous, lanceolate or lance-elliptic 5—8(—11) x 1-2.4 mm, striately 1—11- nerved from base, dorsally either puberulent, or setose, or rarely glabrous, almost always setose- ciliate, persistent. Leaf-stalks including sensitive pulvinus (5-)7-27(-40) mm, at middle 0.4-0.7 mm diam., shallowly grooved ventrally and bearing an ascending spicule ±1-2 mm between the one pair of pinnae; rachis of pinnae 3-8 cm, the interfoliolar segments to 1.2-3.5 mm; lfts 12- 33(-35)-jug., subdecrescent at each end of rachis, the first pair 0.6-2 mm distant from lance-subulate paraphyllidia 0.6-2 mm, the blades linear or linear-lanceolate from obtusangulate base, acute or apiculate, straight or obscurely arched forward, those near mid-rachis (6—)6.5—12(—15) x l-2.3(-3) mm, (4.7-)5-7(-7.5) times as long as wide, all veinless above, the subcentric midrib with 1—2(—3) weak and short posterior nerves either prominulous or merely discolored beneath. Peduncles 4-17(-20) mm; capitula without filaments 5-5.5 mm diam., prior to anthesis either conelike or submoriform depending on length of bracts, these oblanceolate, elliptic-obovate or rhombic-oblanceolate ±1.5-3 mm, beyond middle pectinately setulose-ciliate, mucronate by excurrent midrib, the blade either glabrous or minutely puberulent dorsally; flowers 4-merous 4-androus, some lower ones staminate; calyx (further described under vars.) either minute or asymmetrically paleaceous, not over 1 mm; corollas narrowly funnelform 2-2.8 mm, the ovate cymbiform, strongly keeled but otherwise scarcely thickened lobes 0.65-0.9 x 0.4-0.5 mm, dorsally glabrous or microscopically papillate-puberulent; filaments pick or lilac-pink, exserted (4.5-)5-7.5(-8) mm. Pods of well-fertilized capitula to 10-18, sessile, in profile narrowly oblong (10-) 13-21 (-25) x 4-5 mm, (2-)3- 4(-6)-seeded, the shallowly undulate replum 0.4-0.55 mm wide, abruptly produced at apex into a subulate point 1-1.5 mm and armed with pluri-seriate straight stramineous setae to (2-)2.5- 3.5(-4) mm, the papery, at first green but early brownish-stramineous valves colliculate over each seed, at once puberulent and hispid with suberect setae shorter and more slender than those of replum, when ripe separating from replum and dividing into rhombic or almost square, biconvex indehiscent, free-falling articles 2.5-4.5(-5) mm long; seeds rhombic-obovoid-lentiform 2.9-3.4 x 2.5-2.9 mm, the testa dull brown-olivaceous, often fuscous-spotted.

In overall facies M. polycarpa resembles armed varieties of M. xanthocentra, but is effectively distinguished by a spicule at apex of petioles, by an either minute truncate or asymmetrically paleaceous, not radially symmetrical pappiform calyx, and almost always by glabrous, not gray- puberulent flowers. Bentham’s concept of M. polycarpa expressed in Flora brasiliensis (1876) encompassed all then available examples of M. xanthocentra var. xanthocentra and var. mansii. Burkart’s refined definition of the species (1948) is here adopted, but some internal adjustment is required. Burkart admittedly saw neither the type nor the protologue of M. polycarpa and misapplied the epithet to the subcordilleran Argentine variety herein segregated as var. subandina. He was unaware that the calyx of Kunth’s plant was truncate, like that of east-Argentine var. spegazzinii, not asymmetrically paleaceous like that of var. subandina. The type of M. polycarpa appears almost exactly like average var. spegazzinii, except for relatively few and large leaflets and high-montane Peruvian habitat, remote from the main home of the species in the middle Paraguai basin. Further collections from Peru are required before it can be stated unequivocally that two distinct taxa exist, for it is not impossible that the original M. polycarpa of Humboldt and Bonpland was introduced in the vicinity of the old Inca capital of Cajamarca. The situation in Peru is complicated today by var. redundans (see below) in which the leaf-spicules, leaflets and calyx of var. polycarpa are combined with the one-nerved stipules of sympatric M. incarum. Field observation of var. redundans is much needed. Burkart pointed out that the two varieties of M. polycarpa native to Argentina differ not only in form of the calyx but also in pubescence of the upper face of leaflets, this present in the east but absent in the west. However, much of the Paraguayan material that I refer to var. spegazzinii, because of a minute glabrous calyx, has leaflets hairless above, and Burkart’s reliance on this accessory differential character has proved excessive.