Monographs Details: Mimosa hortensis 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 hortensis Barneby
Synonyms:Mimosa campicola Harms
Description:Species Description - Of unrecorded stature but probably (in context of kindred) a diffuse subshrub, the distantly foliate flowering and fruiting stems finely pilose with erect hairs of different lengths (the longest ±1.5 mm) and randomly armed on their 4-5 ribs with scattered, gently recurved stramineous aculei 1-2.3 mm, the leaves except for puberulent and randomly aculeolate axes glabrous concolorous, the subglobose capitula solitary and paired in the axil of coeval or early hysteranthous lvs. Stipules thinly herbaceous, triangular-lance-acuminate 2-3 x 1-1.3 mm, prominently 1-nerved toward tip, persistent. Leaf-stalks of major lvs 4.5-7.5 cm, the discolored pulvinus nearly 4 mm, the petiole 2-3 cm, at middle 0.5-0.9 mm diam., shallowly 2-grooved, the interpinnal segments 1-2 cm; interpinnal spicules 0; pinnae 3-4-jug., little graduated, the rachis including slender discolored pulvinus 10-18 mm, the interfoliolar segments 1.5-2 mm; lfts (5-)6-7-jug., a little decrescent only at very ends of rachis, the first pair 1.5-2 mm distant from subulate-elliptic paraphyllidia 0.3-0.5 mm, the blades narrowly oblong-oblanceolate obtuse from semicordate base, those at mid-rachis ±5.5-8.5 x 1.7-2.8 mm, all veinless above, beneath weakly 1 (-2)-nerved from pulvinule, the midrib only slightly displaced. Peduncles 13-21 mm, at anthesis filiform, thickened in fruit; capitula without filaments ± 5 mm diam., prior to anthesis moriform, the obtuse lf-buds pilosulous with erect hairs; bracts membranous linear 0.5-0.7 mm, eciliolate; flowers 3-merous 6-androus, only some distal ones (in one capitulum examined) bisexual; calyx membranous glabrous, 0.5-0.8 mm, cleft almost to base into narrowly lanceolate lobes; corolla narrowly vase-shaped, basally constricted, 2-2.3 mm, the ovate, finely 1-nerved lobes ±1 x 0.8 mm; filaments pink, free to base, the longer set exserted 4.5 mm; anthers 0.3 mm. Pods 1-3 per capitulum, ascending, stipitate, the stout stipe 2.5-6 mm, the linear, nearly straight body 5.5-9 x 0.9-1 cm, 6-10-seeded, the shallowly undulately constricted replum 0.5 mm wide, the stiffly papery valves low-convex over each seed, the replum and valves alike hispid overall (more densely so over seeds) with erect tapering tawny setae ±1-3 mm long and minutely retrobarbellate toward apex, the valves when ripe breaking up into free-falling articles 10-12 mm long; seeds disciform 6x5 mm, the testa livid-brown.

Distribution and Ecology - In unrecorded habitat, known only from the type-collection and -locality at ±9°25'S, 40°30'W on the S. Francisco river in n. Bahia, Brazil.— Fl. II-III(-?).

Discussion:

I am uncertain as to the rank properly assignable to this remarkable plant. Its kinship to M. campicola seems very close, but the differences are weighty: lack of interpinnal spicules; lobulate calyx; and in particular the relatively enormous, stoutly stipitate pod densely hispid overall with erect tawny setae minutely barbed above the middle. Similar setae, but smaller and fewer, have been noted in two populations of M. campicola (see discussion above), but these have subsessile pods only 6-7.5 mm wide and proportionately short articles.

Distribution:Brazil South America| Bahia Brazil South America|

Narratives:Mimosa hortensis