Mimosa invisa Mart. ex Colla
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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
191. Mimosa invisa Martius ex Colla, Herb. pedem. 2: 255. 1834.—Typus infra sub var. invisa indicatur.
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Description
Species Description - Profusely microphyllidious prickly vines and scrambling (or when lacking support trailing) shrubs 2-5 m (exceptionally dwarfed to 0.5 m), the 5-ribbed or subterete striate, soft-woody internodes and the ribs of lft-stks armed with files of recurved aculei to 0.5-2 mm and also minutely reddish-granular, otherwise varying from glabrous to the puberulent peduncles to densely pilosulous or subtomentulose with erect or spreading, sordid or whitish plain hairs to 0.2-0.5 mm, the thin-textured, when dry fragile lfts dull brown-olivaceous above, either concolorous or paler beneath, always ciliolate but their faces either both glabrous, or both puberulent overall, or the upper alone glabrous, the narrowly oblong or cylindric capitula mostly 2-4 together either in the axil of coevally expanding or of early hysteranthous lvs, then axillary in fruit, or all or partly exserted from foliage in a permanently efoliate pseudoraceme. Stipules subulate or rarely lanceolate 1.5-5 x 0.2-0.8 mm, 1-nerved, mostly persistent. Leaf-stalks (2-)4-16 cm, the petiole 1—4(—5) cm, at middle (0.5-)0.6-1.6 mm diam., the narrow ventral sulcus either continuous between pairs of pinnae or bridged and then sometimes charged with a small subulate spicule, the interpinnal segments 3-16(-20) mm; pinnae (3-)4-21-jug., proximally decrescent but distally subequilong, the rachis of longer ones 1.4—4.5 (5.5) cm, the interfoliolar segments 0.5-1.9 mm; lfts of longer pinnae 17-50-jug., decrescent at each end of rachis, the small first pair 0.4-1.7 mm distant from subulate paraphyllidia 0.1-0.45(-0.7) mm, the blades linear or obscurely linear-oblanceolate from rectangulate or deeply obtusangulate base, obtuse apiculate or deltately acute at apex, the longer ones (1.8-)2-8(-9) x 0.4-1.6(-l.8) mm, 4.5-6 times as long as wide, all veinless above, dorsally l-2(-3)-nerved from pulvinule, the slender midrib subcentric, immersed but discolored, simple or faintly 1-2- branched on each side, the posterior nerve(s), when present, weak and short. Peduncles 3-16 mm, ebracteolate; spikes without filaments 3-5.5 mm diam., the axis becoming (5-)8-85 mm, the narrowly obovoid obtuse fl-buds either glabrous or distally puberulent; bracts linear-oblanceolate or -spatulate 0.3-0.8 x 0.1-0.25 mm, mostly deciduous; flowers (4-)5(-6)-merous (4-)5-androus, some lower ones of each spike often staminate, all sessile or almost so; calyx campanulate 0.2-0.6 mm, the very short or obscure teeth often granular-ciliolate; corolla membranous, turbinate or narrowly funnelform 1.3-2.7 mm, the erect lance-ovate 1-nerved lobes 0.7-1.2 x 0.4-0.6 mm, subincurved at apex; filaments pink, free to base, exserted (4-)4.5-7(-8) mm; anthers 0.3-0.5 mm, the connective broadly elliptic in dorsal view. Pods 1-3 per spike, in profile broad-linear, when well fertilized 7-14.5 x (0.5-) 1-2.2 cm and (7-) 10-18-seeded, tapering at base into a stipe (1-) 1.5-5 mm, abruptly cuspidate at broadly rounded apex, the randomly retro-aculeate replum 0.4-0.8 mm wide, glabrous or thinly puberulent, the papery, pale brown valves plane except for a small discolored colliculus over each seed, either glabrous but minutely granular or sparsely to densely puberulent overall, when ripe breaking up into free-falling, individually indehiscent oblong articles 6-9(-10) mm long; seeds transverse at middle of valves, not seen fully ripe.
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Discussion
The four species of ser. Spiciflorae lacking petiolar nectaries that were known to Bentham in 1876 (p. 407) together with the subsequently described M. brevispica and M. esmeraldae are essentially homogeneous in structure of flower and pod, and differ in relatively labile characters of leaf-formula, length of flower-spikes, and leafiness of the mature inflorescence. These unstable characters vary independently of one another, with the result that Bentham’s diagnostic phrases no longer apply to much of the material that has accumulated in the past century. The group is here treated as one species that shows a degree of racial differentiation in its farflung range. South of Amazonia the flower-spikes tend to be elongate and the whole inflorescence tends to be exserted from foliage, whereas in Guayana, Venezuela and adjoining Colombia the individual spike is either contracted or relatively few-flowered, and the majority of peduncles are early surpassed by their subtending leaf, the pods consequently immersed in foliage. I recognize these internally variable assemblages as the geographic subspecies invisa and spiciflora, respectively. Within each subspecies there is wide variation in leaf-formula, leaf-size and length of flower-spike, in pubescence of stem and pod, and in width of pod, but these features are insecurely correlated or obviously not so. The visually arresting differences in leaf-formula are rather well linked with dispersal in the range of subsp. in visa, less well in that of subsp. spiciflora, but in both are loosely correlated with length of the floral axis. In spite of ambiguous individual specimens it seems desirable to maintain two varieties in each subspecies, these corresponding more or less closely with the four species known to Bentham.