Monographs Details: Mimosa spirocarpa Rose
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 spirocarpa Rose
Description:Species Description - Stiffly branched macrophyllidious shrubs, randomly armed on some internodes with 1-2 distally recurved broad-based aculei 2-6 mm (some whole branches unarmed), the annotinous stems brown or fuscous lenticellate, the young lvs canescent, the mature ones green but a little paler dorsally, the amentiform fl-spikes mostly 2-4-nate in the axil of coevally expanding lvs on hor- notinous branches, or some distal ones pseudoracemose, together forming a foliate panicle. Stipules linear-attenuate or -ligulate 3—5.5 mm, bluntly or obscurely 1-nerved dorsally, becoming dry but persistent. Leaf-formula iii-vi/2-3, the pinnae distally accrescent, the proximal pair often very short and 2-foliolate, the lf-stk (4-)5- 10 cm, the longer interpinnal segments ± 1.5-2.5 cm, the ventral sulcus continuous between pinna-pairs (spicules 0), the rachis of distal pinnae (1-) 1.5-3.5 cm; lfts accrescent distally, obliquely obovate obtuse, the distal pair of larger lvs 13—28 x 8—23 mm, 1.2-1.9 times as long as wide, all 3—5-nerved from pulvinule, the little-displaced incurved midrib 2—5-branched on each side, the inner posterior nerve expiring near or beyond mid-blade, the rest weak and short, the tertiary venulation 0 or random, the pallid nerves prominulous only beneath. Flower-spikes without filaments 4.5-6 mm diam., the axis including short peduncle 6-10 cm, the bracts linear, less than 1 mm, caducous; fl-buds obovoid, densely silky overall; flowers sessile, 5-merous 10-androus, all bisexual; calyx campanulate 0.8-1.6 mm, the subulate or depressed-deltate teeth 0.2-0.5 mm, often unequal; corolla turbinate 2.2-2.7 mm, the ascending ovate lobes 1-1.2 x 0.65-0.8 mm, 1-nerved; filaments pink fading whitish, united at very base to corolla, exserted 5-6.5 mm. Pods scattered along spike-axis, sessile, in maturation becoming rolled to one side into a tight spiral of 1-1.5 turns in dorsoventral view 7-10 mm diam., the face exterior to the spiral strongly bullate-distended, the interior face correspondingly depressed but elevated over each seed, the replum 0.3-0.4 mm wide, together with the papery valves densely silky-tomentellous overall, the ripe valves breaking up into 5-6 free- falling, individually dehiscent articles 4-5 mm long and 3-4 mm wide, the plumply lentiform seeds 2.2-3 x 1.6-2.2 mm, their testa glossy dark brown.

Distribution and Ecology - In thorn-forest below 300 m, known in characteristic fruiting condition only from centr. and s. Sinaloa, Mexico, but perhaps occurring also at the w. edge of the Balsas Depression in Michoacán (Apatzingán).—Fl. VI-X.

Discussion:

This remarkable species is distinguished with difficulty from M. guatemalensis when in flower, but becomes instantly recognizable in fruit. Two collections seen from Apatzingán in Michoacán closely resemble M. spirocarpa vegetatively, in particular in leaf-formula, but their identity will remain open to question until the matching fruits are obtained.

Distribution:Mexico North America| Sinaloa Mexico North America| Michoacán Mexico North America|