Monographs Details: Mimosa pseudoradula Glaz. ex 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 radula Benth.
Description:Species Description - Functionally herbaceous subshrubs with 1-few simple stems (0.7-)l-2.5(-3) m stiffly erect from a carrotlike or amorphous xylopodium, leafy at base only or at l-4(-5) nodes distant not more than 3 dm from root-crown, passing upward into a simple wandlike lax pseudoraceme or strictly narrowly 1-4-branched panicle of globose capitula, the lower stems, lf-stks and corneous lft-margins either hispid with spreading setae to 25 mm or more shortly scabrous and gray-puberulent with ascending or subappressed trichomes less than 1.5 mm, the upper stems and axes of inflorescence either scabrous-hispidulous or silky-pilose with shorter or finer, in one var. retrorse setae, the ample, firmly papery brown-olivaceous or glaucescent, subconcolorous lfts commonly all glabrous facially, the lower 1-2, rarely all, thinly setose dorsally. Stipules firm, lanceolate or linear-lanceolate 5-12 x 1-2 mm, very early dry and deciduous, absent from many mature specimens. Leaf-stalks of subradical lvs 4-26 cm, at middle 1-2 mm diam., rounded dorsally, openly shallowly sulcate ventrally, those of cauline lvs much shorter (not separately described further); pinnae 1-jug., the rachis of each 3.5-14 cm, the longer interfoliolar segments 10-22 mm; lfts 4-10(-l l)-jug., somewhat decrescent proximally, scarcely so distally, the first pair 3- 7(-10) mm distant from pulvinus or from corneous conic paraphyllidia less than 1 mm, the anterior member less than half as long as the posterior, the proximal pairs of lfts lance-ovate or semi-ovate, the broad distal ones semi-cordate, all very obtuse, the larger blades 2-4.5(-5) x (0.8-)l-2.4(-2.7) cm, 1.8-2.8 times as long as wide, all palmately 5-7-nerved from broad wrinkled pulvinule, the excentric, gently incurved midrib dividing blade ± 1:2-4, the single primary nerve on its anterior side weak, the 3—4 posterior ones incurved-ascending and weakly brochidodrome within the corneous margin, the secondary venulation usually weak and random, all nerves of mature blade immersed or almost so above, prominent beneath. Peduncles always solitary 1-4.5 cm; capitula without filaments (7.5—)8—11 mm diam., prior to anthesis conelike and silky-setose; bracts linear-oblanceolate or -spatulate 1.7—3.5 x 0.3—0.45 mm, densely setulose dorsally and ciliolate; flowers 4-merous 4-androus, some or many of each capitulum staminate; calyx 1.8-3 mm paleaceous, divided to below middle into four lacerate scales, at base with a ring of fine setulae; corolla narrowly funnelform 3.2-4.8 mm, the firm yellowish cymbiform lobes 1.1-2 x 0.45-0.6 mm, glabrous or microscopically papillate externally; filaments pink, monadelphous through 2-2.5 mm around ovary, exserted 6-9 mm. Pods (poorly known) ±3-12 per capitulum, sessile, in profile narrowly oblong 17-25 x 6-7.5 mm, 2-5-seeded, the replum ±0.5 mm wide, shallowly constricted, the stiffly papery valves colliculate over each seed, the replum and valves alike densely hispid-pilose with widely ascending-incurved, tapering or flagelliform setae to 1.5-2.5 mm, the valves when ripe breaking up into free-falling indehiscent articles ± 5-7 mm long; ripe seeds not seen.
Mimosa pseudoradula resembles the closely related M. radula in all details of flower and pod, as well as in outline and venation of the relatively ample leaflets, but differs greatly in habit of growth and disposition of the foliage. Whereas the stem of M. radula is densely clothed up to the inflorescence with mostly sessile leaves, M. pseudoradula has only a few subradical long-petiolate leaves clustered on the xylopodium or at very base of stem; or has at best 1-5 distant, smaller and more shortly, but still evidently petiolate cauline leaves borne at distant nodes below middle of the plant, most of which consists of a virgate or narrowly paniculate inflorescence bare of leaves. The two species next following, M. flavocaesia and M. cyclophylla, are similar in habit but differ much in details of foliage.
The plentiful modem collections of M. pseudoradula fall into well-differentiated pubescence-types, here recognized as varieties. That most prevalent in Distrito Federal, particularly on the Sobradinho and Torto forks of rio S. Bartolomeu, has almost glabrous or puberulent and scaberulous stems often but not always bearing a few cauline leaves, and leaflets margined with a single file of forwardly appressed setae. Outside the Distrito this form, which is described below as var. detonsa, is known from only one collection on the upper Paranã near S. João da Aliança. Less common in the Distrito, but occasionally sympatric there with var. detonsa, is var. pseudoradula, distinguished by long-setose lower stem and leaf-stalks and by elongate setae spreading at wide angles from the leaflet-margin. This extends further outside the Distrito than var. detonsa, south-westward to the Descoberto valley and north to Chapada dos Veadeiros and Niquelândia in central Goiás. Its range contains and greatly exceeds that of var. detonsa. On Serra dos Cristais in southwestern Goiás M. pseudoradula is represented by a population similar to var. detonsa in indumentum of lower stem and leaflet-margin but differing in leaves more definitely radical, shorter, and composed of one or two less pairs of leaflets in each pinna. This differs further from var. detonsa in having the setae of the primary inflorescence-axis sharply retrorse and is thereby easily separated as an endemic var. crystallites. An intermediate type, having the retrorse indumentum of inflorescence and shortly petiolate leaves of var. crystallites but the leaflet- number of var. detonsa, is known from two collections to the west of the Distrito and is with some misgiving described as a distinct taxon, var. anapolitana.