Mimosa puberula Benth.
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Authors
Rupert C. Barneby
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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.
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Family
Mimosaceae
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Scientific Name
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Type
77. Mimosa puberula Bentham, London J. Bot. 5: 88. 1846.—"Zimapan [Hidalgo] in Mexico, Coulter."—Holotypus, K (hb. Benth.)! = K Neg. 16895 = NY photo s.n., dated 1928!
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Description
Species Description - Of unknown stature (but arborescent according to protologue), the young flowering branches unarmed, these and foliage densely puberulent with fine whitish hairs 0.1-0.2 mm mixed with reddish granules, the plane thick-textured lfts brown when mature and dry, then thinly puberulent on both faces and dotted beneath with minute immersed yellowish glands scarcely 0.1 mm diam., the dense fl-spikes solitary and geminate, shortly pedunculate in the axil of coevally expanding lvs. Stipules erect, linear-attenuate 4-5 x 0.5 mm, nerveless externally. Leaf-formula vi-vii/16-17, the lf-stk 5-6 cm, the petiole ±6-7 x 1 mm, the interpinnal segments 7-10 mm, the ventral sulcus bridged between pinna-pairs but espiculate; rachis of longer pinnae 35-43 mm, the interfoliolar segments 2-2.5 mm, the lfts subequilong except at very end of rachis, the first pair 1-1.5 mm distant from erect paraphyllidia 0.2-0.4 mm, the blades oblong-elliptic obtuse from bluntly auriculate base, the longer ones 4.5-5.5 x 1.7-2 mm, all veinless or almost so above, beneath 2-nerved from pulvinule, the weakly prominulous midrib dividing blade ±1:2, the posterior nerve expiring near or beyond mid-blade. Peduncles stout ± 5-9 mm, bracteate near middle; spikes without filaments ±6 mm diam., the axis 2-3 cm; bracts linear, less than 1 mm, deciduous; flowers either 4- or 5-merous diplostemonous; calyx campanulate ±1x1 mm, thinly puberulent externally, the rim denticulate, the teeth not over 0.2 mm; corolla turbinate ±2.5 mm, the ovate acute 1-nerved lobes ±1x1 mm; filaments free or nearly so, exserted 4.5 mm; style attenuate at apex; ovary pilosulous; pod unknown.
Distribution and Ecology - In unrecorded habitat, known only from the type-collection, reputedly from the upper Moctezuma valley, near 20°45'N, 99°30'W, in Hidalgo, Mexico.
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Discussion
Mimosa puberula differs from all spicate Mexican mimosas other than M. tenuiflora in dorsally gland-dotted leaflets, and from this in partly pentamerous flowers, minute erect, not cucullately incurved calyx-teeth, and simply pilosulous, not pilosulous and glandular ovaries. The pod, when discovered, may provide further differential characters. The type is unarmed, but it would be no surprise to learn that older branches are armed like those of M. tenuiflora. Whether pentamerous or tetramerous flowers prevail in the species will bear on interpretation of the affinities of the species, at present indecipherable. If the locality at Zimapán, near 1800 meters on the Gulf slope of Sa. Madre Oriental, is correct, the ecology of the species must be very different from that of M. tenuiflora, which enters Mexico from the south only in lowland thorn-scrub in Pacific Chiapas and Oaxaca. Mimosa puberula is here provisionally referred to ser. Leiocarpae. No compatriot spicate species appears at all close to it.
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Distribution
Mexico North America| Hidalgo Mexico North America|