Monographs Details: Mimosa stylosa 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 claussenii var. prorsiseta Barneby
Description:Species Description - Shrubs 0.7-2 m with extremely ample multi-pinnate and multifoliolate lvs, the homotinous stems, lf-stks and axes of early elongating, hysteranthously foliate pseudoraceme of plumply ellipsoid capitula hispid with fine flagelliform brownish setae to 3-5 mm long and at dilated base to 0.2-0.3 mm diam., those of the stems proximally retrorse, thence incurved-ascending, the lfts facially glabrous, setose-ciliolate. Stipules firm, lance-acuminate 8-14 x 1.5-3 mm, glabrous castaneous within, readily disjointing. Leafstalks 15-33 cm, the petiole almost 0 or to 2-3.5 cm, the longer interpinnal segments 8-20 mm; spicules 0; pinnae 20-28-jug., the rachis of longer ones (2.5-)3-8 cm, the longer interfoliolar segments 1-1.5 mm; lfts of longer pinnae 35-63- jug., the first pair next to pulvinus, the blades linear-oblong obtuse apiculate, the longer ones 5-7 x 0.9-1.5 mm. Primary axis of pseudoraceme 2-4.5 dm; peduncles 1-3 per node, 2-3 cm; capitula without filaments 14-25 x 11-13 mm, prior to anthesis conelike and densely hispid; bracts oblanceolate 4-6 x 0.8-1.2 mm, coarsely setose dorsally, eglandular; flowers 4-merous 8-androus, the lower ones staminate; calyx 0.50.7 mm, glabrous externally, the chaffy cilia to1-2 mm; bisexual corollas 5-6 mm, the tube glabrous, the lobes dorsally setulose; filaments pink, monadelphous through 1-1.5 mm around base of pilosulous ovary, the longer ones exserted 11-16 mm; style 22-28 mm, surpassing the longer filaments by 5-9 mm. Pods (described from annotinous sample) 1-several per capitulum, sessile, in profile oblong-elliptic 25-30 x 11-12 mm, the replum at broadest point 2.5-3.5 mm wide, distally contracted into a stout conic cusp 2 mm, the valves when ripe separating entire from replum, the livid exocarp to 0.4-0.5 mm and crustaceous endocarp 0.1-0.15 mm thick in section, the replum and valves alike hispid with setae of different calibers separated by distinct though narrow interspaces, the coarser setae erect-incurved to 1.5-2 mm long, at base 0.45-0.6 mm diam., those of replum a little shorter; ovules 58; seeds not seen.
Distribution and Ecology - In cerrado near 900 m, known only from the type-locality on headwaters of rio Jequitinhonha e. of Diamantina and from Sa. do Cipó, between lat. 18°20' and 19°30'S in centr. Minas Gerais.— Fl. III-IV, fr. persistent on dead stems into second year.
Mimosa stylosa is closely akin to M. claussenii, resembling its var. prorsiseta in habit and vesture and its var. corneiseta in leaf-formula and vesture but less so in habit. It differs from M. claussenii sensu lato in shorter peduncles and vesture of the pod, of which the livid exocarp is visible between relatively short setae and not concealed by a long dense fleece. Related species known to occur in Sa. do Espinhaço either have much shorter leaf-stalks, shorter pinnae, or both (M. foliolosa vars.) or, if the leaves are similar in size and formula (M. albolanata var.) they are borne on abbreviated stems arising from a subsessile terrestrial woody pediment. None of these shares with M. stylosa the elongated style which projects 6-9 mm beyond the longer set of filaments. The material from Sa. do Cipó (Joly & al. 1748, E) differs from that from near Diamantina in subobsolete true petioles, somewhat shorter pinnae, and more fugacious stipules, but otherwise agrees well with the type. Mimosa foliolosa var. pachycarpa, the mimosa of this series common and repeatedly collected on Sa. do Cipó, is readily distinguished from M. stylosa by fewer leaflets (to 20-26, not 35 or more pairs per pinna), and small capitula (without filaments 7-8, not 11-13 mm diam.).
Distribution:Brazil South America
| Minas Gerais Brazil South America