Monographs Details: Mimosa gatesiae Barneby
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 gatesiae Barneby
Synonyms:Mimosa gracilis Benth. var. gracilis
Description:Species Description - Delicate small-lvd unarmed perennial herbs, glabrous except for minutely ciliolate stipules and pinna-rachises, the wiry, mostly simple stems 13 dm, 0.5-1 mm diam., ascending in a dense tuft from a knotty caudex either terminating or lateral to an oblique woody rootstock to 5 mm diam. or from a thick-topped xylopodium, the globose capitula axillary to and ± equalling the distal lvs, or a few furthest ones forming a shortly exserted pseudoraceme. Stipules ovate or lanceolate 0.8-1.5 mm, 1-nerved, persistent. Leafstalks capillary 10-22 mm, the petiole 5—14(—16) mm, at middle 0.2-0.3 mm diam., the longer interpinnal segments 3-5.5 mm; between each pair of pinnae a minute deltate-apiculate spicule; pinnae 2-4-jug., the retroarcuate rachis 3-7 mm; lfts of longer pinnae 6-8-jug., subaccrescent distally, the first pair 0.5-0.7 mm distant from subulate paraphyllidia, in outline narrowly oblong or oblong-obovate, straight or subincurved, at apex obtuse apiculate, the larger ones 2-4 x 0.6-1.1 mm, the blades almost or quite veinless externally. Peduncles capillary, solitary or geminate 10-18 mm; capitula without filaments 3.5-4.5 mm diam., prior to anthesis moriform; bracts elliptic-obovate 0.5-0.7 mm, minutely glandular-ciliolate; flowers 4-merous 8-androus glabrous, the lowest staminate and slightly smaller, the rest bisexual; calyx 0.4-0.65 mm, shallowly 4-denticulate; corolla broadly turbinate 1.7-2.5 mm, the ovate 1-nerved lobes 1-1.2 mm; filaments either pale or vivid pink, monadelphous through 0.4-0.5 mm, exserted 2.5-4 mm; ovary glabrous; pod unknown.

Distribution and Ecology - In moist campo rupestre near 1100 m, apparently local on Chapada dos Veadeiros in e.-centr. Goiás and on the headwaters of rio Torto in Distrito Federal, Brazil.—Fl. II—III.

Discussion:

This elegant dwarf mimosa was first collected in 1895 "entre Bananal et le Rio Torto" in the present Federal District by Glaziou (no. 21059, P!), growing with or close to the related M. gracilis var. brevissima (no. 21058, G, K!). Glaziou not only confused these two species, but misidentified both (1906: 182) as M. paucifolia. This allopatric relative differs from M. gatesiae in junceous growth-form, in much longer leaf-stalks (±2-8, not 1-2 cm), and in leaf-formula (i—iii/2-3, not ii-iv/6-8). From undeniably similar and partly sympatric M. gracilis var. brevissima the new species differs in more numerous leaflets (to 6-8, not 2-5 pairs), in characteristically recurved pinnae, and in the deltate interpinnal scale in place of a subulate spicule.

It is my pleasure to dedicate this species, with respect and affection, to Dr. Bronwen Gates, author of an esteemed monograph of Banisteriopsis (Fl. Neotrop. Monogr. 30. 1982), who participated in its discovery on Chapada dos Veadeiros.

Distribution:Brazil South America| Distrito Federal Brazil South America|

Narratives:Mimosa gatesiae