Monographs Details: Mimosa bombycina 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.
Synonyms:Mimosa pogocephala Benth.
Description:Species Description - Erect unarmed shrubs attaining 2 m, with 1-few virgate defoliate trunks and coarse fewleaved, simple or once forked homotinous branches ±2.5-4 mm diam. densely silky-lanate with extremely fine entangled, gray flagelliform setae to 2-5 mm, the lvs similarly but less densely lanate beneath, finely puberulent above, discontinuously setose-ciliate, the densely pilosulous capitula either axillary to distal lvs and forming a subcorymbiform leafy-bracteate pseudoraceme or serial in many successive lf-axils along hornotinous branches. Stipules firm, broadly or narrowly lanceolate 4.5-10 x 1.5-2 mm, densely lanate externally their whole length or merely scabrous distally, glabrous within, tardily deciduous. Leaf-stalks stout 5-15 mm, enveloped in silky wool, the ventral groove shallow; pinnae 1-jug., their axis 5-8 cm, the longer interfoliolar segments 4-7.5 mm; lfts 9-16-jug., a little decrescent upward from near mid-rachis, the first pair 1.5—4 mm distant from lanceolate paraphyllidia 1-2 mm, the blades obliquely elliptic or oblong-elliptic from broadly semicordate base, abruptly apiculate, those at mid-rachis (11 —) 13— 25 x 4-10 mm, 2-2.8(-3) times as long as wide, all 4-5 nerved from pulvinule, the straight midrib dividing blade 1:1.3-2, either simple or giving rise on each side to 3-5 secondary venules, the midrib and posterior nerve coarsely prominulous on lower face of lfts, the rest weaker. Peduncles in fruit 1.5-3 cm; capitula (not seen at anthesis) apparently ovoid and without filaments ±9-10 mm diam.; bracts narrowly lanceolate 2.5-3 x 0.4 mm, densely silky-setose dorsally from base upward; flowers 4-merous 4-androus; calyx shallowly campanulate ±0.2 mm, the rim obscurely undulate glabrous; corolla subcylindric 3.1-4.2 mm, the concave but scarcely thickened lobes 0.8-1.2 x 0.5-0.6 mm, silky-pilosulous externally at tip; filaments (pink?) free, exserted ±6.5 mm. Pods ±2-12 per capitulum, sessile, in profile oblong-elliptic or broadly oblanceolate, without indumentum 14-17 x 6-6.5 mm, compressed but turgid, the straight replum 0.7-0.9 mm wide, produced at apex into a conic point, the ripe valves colliculate over each of (3-)4 seeds, differentiated into livid exocarp and crustaceous endocarp each less than 0.1 mm thick in section, when ripe separating in one piece both from the replum and from each other, the replum and valves alike concealed by fine smooth, pale silvery-brown setae attaining with their flagelliform tip 2.5-4.5 mm, the endocarp produced between seeds as a hyaline transverse septum to ± 1 mm wide; seeds plumply obovoid or variably distorted by pressure from the endocarp, 3.5-5 x 2.3-3.3 mm, the testa dull, fuscous or soot-black, smooth or minutely punctate, the convex lens paler.
Mimosa bombycina, one form of which, discovered by Glaziou near Diamantina, was recognized by Taubert as undescribed but never formally published, is related to the vicariant M. pogocephala. It differs in fewer, larger leaflets, somewhat thicker capitula, minute glabrous calyx, and especially in the densely silky, not hispidly bur-like pod. It is known from two highly localized populations which appear varietally distinguishable.