Monographs Details: Mimosa bocainae 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 bocainae Barneby
Synonyms:Mimosa itatiaiensis Dusén, Mimosa reduviosa Barneby
Description:Species Description - Slender unarmed microphyllous shrubs of unrecorded stature, the distally much branched homotinous stems densely clothed with narrow crowded, forwardly imbricate, V-form lvs and densely shaggy-pilose, especially toward flowering nodes, with fine, loosely deflexed and thence inwardly curved or flexuous, densely scaberulous rufescent setae to ± 1-1.5 mm, the lf-stks subappressed-pilose with straighter, smoother setae, the brown-olivaceous subconcolorous lfts glabrous facially, weakly discontinuously setulose-ciliolate, the narrowly ellipsoid capitula on shaggy-pilose peduncle ± as long as subtending lf, the whole inflorescence either simply or paniculately pseudoracemose, the pods persistent on defoliate annotinous stems below the new foliage. Stipules firm erect, linear-attenuate 3.5-7 x 0.3-0.5 mm, setose dorsally, glabrous within, 1 -nerved, persistent. Leaf-stalks including hard pulvinus 1.5-2 mm; pinnae 1-jug., the rachis of each 20-35 mm, the interfoliolar segments 0.65-1.2 mm, low-carinate and obscurely excavate ventrally; lfts 25-33-jug., subdecrescent at each end of rachis, the unequal first pair ±0.5 mm distant from pulvinus (paraphyllidia not differentiated), the blades of all linear from obtusely auriculate base, obtuse at apex, those near mid- rachis (3.2-) 3.5-6 x 0.35-1 mm, ±5-7 times as long as wide, the shallowly concave ventral face veinless, the dorsal face weakly 2-nerved from pulvinule (a posterior third nerve, if present, short and obscure). Peduncles (8-) 12-27 mm; capitula without filaments 7.5-12 x 4.5-5.5 mm, prior to anthesis moriform, the weakly 4-carinate fl-buds distally gray-pilosulous; bracts linear-lanceolate 1.5-2 x 0.2-0.3 mm, glabrous 1-nerved dorsally, setose-ciliolate; flowers 4-merous 4-androus, mostly bisexual; calyx including pappiform setae 0.8-1.2 mm, the shallowly campanulate, obscurely lobulate tube 0.3-0.6 mm, the cilia not confluent at base; corolla 2.2-2.7 mm, that of lower fls narrowly turbinate, that of upper fls subcylindric, the ovate, scarcely thickened lobes 0.6-0.8 x 0.5-0.6 mm; filaments pink (drying yellowish), free to base, exserted 5.5-7.5 mm. Pods several per capitulum, sessile, in profile oblong or oblong-elliptic 7-17 x 4-7 mm, 1-2- seeded, the replum 0.7-1.1 mm wide, hispid with stiff straight erect pluriseriate setae to 4-5 mm, the papery valves colliculate and weakly setulose over each seed, otherwise glabrous, breaking up when ripe into individually dehiscent articles ±4.5-5 mm long, these free-falling but often imprisoned by interlocking setae of replum; ripe seeds not seen.

Distribution and Ecology - On rocky stream banks and in moist campo near 1700 m, sometimes forming pure thickets, known only from Sa. da Bocaina and its immediate environs, just within the Tropic of Capricorn in the e. lobe of S. Paulo, Brazil.—Fl. X- XII(-?).

Discussion:

Mimosa bocainae and M. reduviosa are sibling species, suggestively similar in life-form and ecology, in loosely retrorse and scabrous cauline setae, and in form of the craspedium, but are seemingly distinct in several coordinated characters supported by vicariant distribution. The diagnostic characters of M. bocainae are linear one-nerved stipules, immarginate leaflets with only two long dorsal nerves, and ellipsoid, not globose capitula. Mimosa itatiaiensis, which replaces M. bocainae on nearby Mt. Itatiaia, differs from both of these in forwardly ascending, smooth cauline setae and in very small membranous, minutely ciliolate (not pappiform) calyx.

Distribution:Brazil South America| São Paulo Brazil South America|

Narratives:Mimosa bocainae
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