Monographs Details: Mimosa gentryi 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 gentryi Barneby
Synonyms:Mimosa barrancana Gentry, Mimosa moniliformis (Britton & Rose) R.Grether & Barneby
Description:Species Description - Virgate shrubs attaining 2-3 m, with long straight pliant smooth castaneous branches armed at nodes with a pair of almost straight, widely ascending infrastipular aculei 2-5 mm, except for residually ciliolate young lfts glabrous throughout, the foliage olivaceous concolorous, the inflorescence a narrow thyrse of hemispherical capitula in a succession of lf-axils on peduncle much longer than subtending lf-stk, and a few capitula from brachyblasts on annotinous stems well below the current thyrse. Stipules erect, setiform (1—)2—4.5 mm, persistent. Leaf-stalks 1.5-17 mm, the petiole 1.5-5 mm, sometimes reduced to the slender wrinkled pulvinus, the single interpinnal segment or the longer of two 3-10 mm, the ventral sulcus continuous (spicules 0), the terminal appendage setiform; pinnae 1-3-jug., the distal pair a little longer, the rachis of longest ones 4-26 mm, the longer interfoliolar segments (1 —) 1.5—5.5 mm; lfts 3-6-jug., the first and last pairs shorter, the blades oblong- or ovate-elliptic from oblique base, acuminulate, those at mid-rachis 4-9 x (1.2—) 1.8—3.5 mm, 1.7-3.3 times as long as wide, all veinless above, beneath 2(-3)-nerved from pulvinule, the midrib a little displaced, simple, the inner posterior nerve expiring at or below mid-blade, the outer one short or obsolete. Peduncles 1-2 per node, 12-28 mm; capitula without filaments 7-8 mm diam., prior to anthesis moriform, the receptacle ±1-1.5 mm; bracts shorter than calyx, early deciduous; flowers randomly 4- and 5-merous, diplostemonous; calyx membranous campanulate 0.8-1 mm, the tube glabrous, the teeth scarcely 0.1 mm, the orifice minutely ciliolate; corolla narrowly funnelform 2.5-4.3 mm, the ovate or lanceolate, distally recurving lobes ± 1-1.3 x 0.55-0.9 mm; filaments lilac, exserted 4.5-6 mm. Pods 1-3 per capitulum, in profile undulately linear, gently decurved, the whole 30-45 x 5-6 mm, 4-6-seeded, attenuate at base into a stipe ± as long as calyx and at apex into a cusp 1.5-2.5 mm, the shallowly constricted, unarmed replum 0.4-0.5 mm wide, the stiffly papery, brownish sublustrous, faintly venulose glabrous valves elevated over each seed as a longitudinal colliculus, when ripe separating, primarily along abaxial side, from the replum in one piece, the cavity continuous; seeds basipetal, compressed-ellipsoid 4.5-5 x 2.5-2.8 mm, the testa fuscous dull.

Distribution and Ecology - In pine-oak forest and oak-savanna, ±9001300 m, known only from Sas. Charuco and Tecurahui on the río Fuerte—río Mayo divide in s. w. Chihuahua and adj. Sonora, and from Sa. Surutato near 25°40'N in n.-e. Sinaloa, Mexico. -Fl. VII-VIII(-?); fr. X(-?).

Discussion:

The type-collection of M. gentryi was misiden- tified by Standley (in herb.) as M. lindheimeri A. Gray, but was not mentioned as such in Gentry’s report on the plants of Río Mayo. A later collection (Gentry 6594, NY) from Sa. Surutato was distributed as M. pringlei. While this last is certainly of the same group, the truly close kindred of M. gentryi are M. barrancana and M. moniliformis, vicariant south- and north-ward respectively low on the Pacific slope of Sa. Madre Occidental. From each of these M. gentryi differs in abbreviated leaf-stalks and few pinnae. The only shallowly constricted pod is almost that of M. barrancana. Mimosa pringlei, a species native at the lower edge of the oak-forest on the east slope of Sa. Madre, has similar leaf-formula but differs greatly in stiff xeromorphic life-form and hispidulous flowers.

Distribution:Mexico North America| Sonora Mexico North America| Sinaloa Mexico North America| Chihuahua Mexico North America|

Narratives:Mimosa gentryi