Monographs Details: Mimosa pabstiana 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 pabstiana Barneby
Synonyms:Mimosa ceratonia var. pseudo-obovata (Taub.) Barneby, Mimosa diplotricha C.Wright ex Sauvalle, Mimosa invisa Mart. ex Colla
Description:Species Description - Prickly shrubs attaining 2 m, armed along the 5scarcely prominulous ribs of older efoliate stems and homotinous leafy branchlets with scattered decurved broad-based aculei to ± 1.5-2 mm, and along dorsal rib of lf-stks with similar but smaller ones ±0.5 mm, appearing glabrous but the stems, lf-stks and the dorsal face and margin of lfts minutely puberulent, nowhere glandular, the thin-textured plane lfts bicolored when dried, brown-olivaceous above, paler beneath, dull on both faces, the globose capitula (1—)2—3 together both in axil of coeval lvs, when early immersed in foliage, and pseudoracemose-paniculate, when exserted up to ±1.5 dm. Stipules erect setiform 3-6 x 0.3-0.5 mm, prominulously 1-nerved, persistent. Leaf-stalks of main cauline lvs 3-8.5 cm, the petiole 8-16 mm, at middle 0.4-0.9 mm diam., the longer interpinnal segments 5-12 mm, the ventral groove interrupted between pinna-pairs by a stiff acicular spicule 0.6-1.2 mm; pinnae (4-)5-7-jug., a little accrescent distally, the rachis of distal pair 21-33 mm, the longer interfoliolar segments ±1.5-2 mm; lfts of distal pinnae (12-) 13-17-jug., little graduated, the first pair 0.5-1.2 mm distant from stiff subulate paraphyllidia 0.2-0.8 mm, the blades oblong or oblong-obovate from obtusangulate base, obtuse but abmptly apiculate, the longer ones 5-6.5 x (1.2—) 1.5—2.5 mm, all veinless above, beneath weakly (l-)2-nerved from pulvinule, the scarcely prominulous midrib subcentric, the posterior nerve very short, secondary venulation imperceptible or indistinctly discolored and immersed. Peduncles ± 1-2 cm; capitula without filaments 5-5.5 mm diam., prior to anthesis moriform; bracts linear-spatulate 0.4-0.7 x 0.1-0.2 mm, minutely ciliolate; pedicels 0.1-0.2 mm; flowers 3-merous 6-androus glabrous, mostly bisexual or some lower ones staminate; calyx campanulate 0.5-0.7 mm, the rim subtruncate; corolla 2.2-2.8 mm, narrowly turbinate, the membranous ovate 1-nerved, almost plane lobes 0.9-1.1 x 0.7-0.9 mm; filaments white (or pink t. Glaziou), free or briefly united into a stemonozone below the ovary, exserted 3.5-6 mm; ovary puberulent after fertilization. Pods (described from annotinous remains) sessile, in profile narrowly oblong, a little decurved, ±30 x 5 mm and ±8-seeded, the replum to 0.8 mm wide, armed along all 3 keels with stout erect aculei to 1-1.8 mm, the firm venulose brownish-stramineous valves also aculeate, the free-falling articles ±4 mm long.

Distribution and Ecology - In unreported habitats, to be sought in thickets and along forest-margins or waysides, known only from scattered stations (type-locality; Sta. Barbara) on the e. slope of s. Sa. do Espinhaço, between ±19° and 20°S in s.-e. Minas Gerais, Brazil. -Fl. XII-?

Discussion:

The flowers of M. pabstiana were recorded unequivocally by Pabst and Pereira as white. Glaziou (1906, l.c. sub M. invisa) called them pink, but this may well refer only to the truly pink flowers of genuine M. invisa, with which he had his nos. 13777 and 12641 confounded. The supposedly pink flower at first suggested a possible affinity to M. diplotricha, but M. pabstiana differs decisively from this in relatively short petioles and trimerous flowers. In habit it is reminiscent of also trimerous ser. Ceratoniae, but it differs gravely from these in leaf-formula and narrow craspedia. Its true affinity seems to lie with M. campicola, similar in everything except as specified in the key to ser. Campicolae.

The epithet celebrates and commemorates the late Dr. Guido Pabst, who befriended H. S. Irwin during his years of botanical exploration on the Brazilian Planalto, and to whom the New York Botanical Garden is indebted for invaluable gifts of rare and unusual Leguminosae from southeastern Brazil.

Distribution:Brazil South America| Minas Gerais Brazil South America|

Narratives:Mimosa pabstiana