A New Species of Mimosa (Leguminosae) from the State of Guerrero, Mexico

Abstract

Mimosa xochipalensis, a new species from the State of Guerrero, Mexico is described and illustrated. It presently is known only from the vicinity of Xochipala, located in the Balsas River Basin in the region known as Cafi6n del Zopilote. The new species is referred to the series Leptostachyae, section Habbasia. It is related to Mimosa rosei Robinson, M. spirocarpa Rose, M. guatemalensis (Hook. & Arn.) Benth., and M. egregia Sandw. About a hundred species of Mimosa are known to occur in Mexico, mainly in tropical and arid regions, although several species grow in temperate areas. The number of species occurring in the country has not changed greatly due to the discovery of several undescribed species in the last years, balanced by recently established synonymies (Grether 1987). Mimosa xochipalensis is one of the recent discoveries. Mimosa xochipalensis R. Grether, sp. nov. (fig. 1).-TYPE: Mexico, Guerrero, Municipio de Zumpango del Rio, 10 km al E-SE de Xochipala, camino a Filo de Caballo, alt. 760 m, selva baja decidua, 22 Nov 1985, Grether 1982 & Quero (holotype: MEXU; isotypes: BM, ENCB, GH, MO, NY, UAMIZ, UC, US, XAL).-PARATYPE: 10 km al E-SE de Xochipala, camino a Filo de Caballo, 19 Nov 1978, Grether 1144 & Quero (ENCB, FCME, MEXU, NY, UAMIZ). Arbor parva (vel frutex), 2-5 m alta, ramis inermibus vel armatis et tomentosis, glabrescentibus; pinnae 1-2-jugae; foliola 1-juga, oblique orbicularia vel reniformia vel obovata, (1)1.5-2.5(3.5) x (0.8)1.2-2.4(3.6) cm, glabra, venatione utrinque manifeste palmato-reticulata. Flores tetrameri vel pentameri, diplostemonei, tomentosi, in spicis brevibus dispositi, axe florali 2-3 cm longo. Leguminis valvulae (2)4-8(9) articulatae, tomentosae, replo inermi. M. rosei Robinson affinis, a qua pinnis 1-2 jugis, foliolis cartilagineis, spicis brevibus, et floribus et leguminibus tomentosis differt. Small, deciduous tree or shrub, 2-5 m high; branchlets ribbed, reddish, tomentulose, and glabrescent, older branches striate, ochre to grayish-brown and glabrous, unarmed or armed with scattered, straight to recurved, internodal aculei. Stipules (0.15)0.2-0.4(0.5) cm long, subulate to linear, tomentose to glabrous, with a prominent central nerve; petiole (1)2-3.5(4.5) cm long, eglandular, grooved, unarmed, puberulous to glabrous; pinnae 1-2 pairs; leaflets 1 pair (exceptionally 2 pairs, seen only in one leaf), (1)1.5-2.5(3.5) cm long, (0.8)1.2-2.4(3.6) cm wide, obliquely orbicular to reniform or obovate, glabrous, cartilaginous, with prominent palmate-reticulate nerves on both faces, margin thickened, continuous, apex obtuse, rarely emarginate; primary leaf rachis (in leaves with 2 pairs of pinnae) (1)1.5-2(3.5) cm long, unarmed or rarely armed with 1-2 aculei; secondary leaf rachis (0.8)1-2(3) cm long, unarmed. Flowers sessile, spicate, the spikes dense, axillary, in groups of 2-3, and arranged in lateral racemes 25-60 cm long; peduncle (1)2-3(3.5) cm long, ribbed, tomentose, unarmed, becoming ligneous in fructification, floral axis 2-3 cm long; bracteoles spatulate, tomentose, uninerved, subequal calyx length, 0.08-0.15 cm; calyx campanulate, 4-5 toothed, tomentose, 0.1-0.15 cm, 1/31/2corolla length; corolla 4-5-lobed, pink, tomentose, 0.2-0.3 cm long, lobes 1/4-1/2 corolla length; stamens 8-10, free to base, 0.7-0.9 cm long; pistil 0.8-1.2 cm long, ovary stipitate, tomentose, 0.05-0.1 cm long, style 0.75-1.1 cm long, stigma poriform. Legume sessile to slightly stipitate, narrowly oblong, (2.5)3.5-6.5(7.5) cm long, 0.6-0.9(1) cm wide, constricted between seeds, stipe 0.3-0.5 cm, valves tomentose, (2)4-8(9) articulate, replum unarmed, tomentose, apex apiculate to rostrate. Seeds ovoid or obliquely rhombic, reddish-brown, 3.5-4.5 x