Mimosa foliolosa

Title

Mimosa foliolosa

Author(s)

Rupert C. Barneby

Scientific Name

Mimosa foliolosa Benth.

Description

227. Mimosa foliolosa Bentham, J. Bot. (Hooker) 4: 406. 1842.—Typus infra sub war. foliolosa (p. 373) indicatur.

Erect unarmed, usually slender shrubs and subshrubs (4-)6-15, less often 30(-50) dm tall, the homotinous stems usually few-branched and each branch passing upward into a pseudoraceme of mostly small capitula exserted ±5-20 cm from foliage; the stems, lvs and inflorescence charged with duplex vesture of fine short pallid villi and either weak erect-incurved or coarser, widely ascending to subappressed yellowish-rufescent setae attaining (0.5-)l-6 mm in length and at base 0.1-0.3, rarely 0.5-0.6 mm diam., these two primary components of vesture independently variable in length and density and often intermingled with random (many) gland-tipped setulae, the lfts either glabrous or villosulous on faces, thinly setulose-ciliolate or less often eciliolate. Stipules firm, narrowly ovate- or lance-acuminate 3-6.5(-9, exceptionally 12) x (0.5-)0.7-3.5 mm, in var. rigens triangular-acuminate to 6 mm wide, all glabrous within, subpersistent. Leaf-stalks of major cauline lvs (4.5-)6-l 9(-21) cm, the petiole including obese insensitive pulvinus 2-7 mm, the longer interpinnal segments (2-)2.5-12 mm; interpinnal spicules 0; pinnae of longer lvs (10-) 12-39-jug., or in vars. foederalis and vernicosa only 7-15-jug., decrescent proximally and less or scarcely so distally, the rachis of longer ones (6-)9-45(-55) mm, the longer interfoliolar segments 0.3-2 mm; lfts of longer pinnae (12—) 16—44-jug., in outline narrowly oblong or oblong-elliptic obtuse, the longest 1.5—6(—8) x 0.3-2.4 mm, either 2-3-nerved dorsally or venation scarcely perceptible. Peduncles solitary and geminate (1-) 1.5-3, rarely 5-7 cm; capitula squatly ovoid-ellipsoid or subglobose, without filaments 7-13(-20) x 6-12(-14) mm, prior to anthesis either conelike or moriform, the receptacle usually less than 8 mm, rarely to 20 mm long; bracts narrowly spatulate-oblanceolate, those at and beyond mid-capitulum 2-6.5 x 0.4-1.1 mm, all dorsally setulose and setose-ciliolate; flowers 4-merous 8-androus, the proximal ones either staminate or degenerate; calyx including a fringe of cilia 0.8—1.3(—1.6) mm, the subtruncate tube 0.25-0.45 mm, either glabrous or beyond middle externally strigulose; corollas mostly 2.5-5.5, rarely 6-6.5 mm, the ovate 1-nerved lobes 0.8-1.2 mm, scarcely callous apically, dorsally pilosulous or strigose-setulose; filaments pink, shortly connate below ovary, exserted 6-10 mm. Pods usually 1-3, rarely to 10 per capitulum, sessile or almost so, in profile oblong or oblong-elliptic (15-)20-55 (in var. gravida to 85) mm long and (6—)7—14(—15, in var. corpulenta 16-18) mm wide, the replum 1.4-3.5(-4, in var. corpulenta 6-7) mm wide, produced at apex into an erect cusp 1—4 mm, the stiffly chartaceous or coriaceous valves densely or thinly villosulous and also coarsely, at times only remotely strigose or hispidulous with comma-shaped setae less than 1 mm, or rarely concealed by a fleece of finer, forwardly subappressed setae, rarely also viscid-villosulous, when ripe separating entire from replum except at very base, recurving from base to release the 7—12(—13) seeds.

The foregoing description records the limits of variation observed in the swarm of closely related microspecies that I here evaluate as varieties of a polymorphic M. foliolosa. Their collective range extends over much of the Brazilian Planalto where they form a network of vicariant forms, each often sympatric with a variety of M. albolanata, or of M. claussenii, or of both. These three complexes are built up by accretion about three distinct general types, but I have found no one infallible criterion by which every member of each can be referred to its group. Each criterion that is useful in one context fails in another, so that it could be argued that the three complexes run together in a continuous fabric of variation. Field observation and experimental work is needed to determine whether or not this is the case, but to combine all three complexes under one specific heading would defeat the aims of classification, for it would assign to one megaspecies plants radically dissimilar in appearance, in detail, and in geographic dispersal.

Ideally, M. foliolosa sensu lato has a distinctly shrubby growth-form, relatively narrow stipules, an extended foliate stem-axis below the pseudoraceme yet raised (in mature individuals) on a framework of defoliate older branches, relatively short pinnae and small leaflets, and relatively small, shortly pedunculate capitula. By contrast, M. albolanata sensu lato has a virgate growth-form with leaves at anthesis mostly crowded below mid-stem (but the inflorescence often hysteranthously foliate), the leaves themselves ampler, and the plumper capitula composed of longer flowers, but not different in length of peduncles. Mimosa claussenii varies in habit between the growth-forms just described, but has broad stipules and either very ample leaves consisting of long pinnae and long leaflets, or large capitula borne on long peduncles, or some combination of these characters. Departures from the idealized state of each character are frequent, as will be evident from the serial and infraspecific keys. In assigning a particular plant to one of these three complexes I have been obliged to make arbitrary decisions which are obviously open to dispute or correction.