Mimosa regnellii

Title

Mimosa regnellii

Authors

Rupert C. Barneby

Scientific Name

Mimosa regnellii Benth.

Description

300. Mimosa regnellii Bentham, Linnaea 22: 529. 1849.—Typus infra sub var. regnellii indicatur.

Erect, amply microphyllidious unarmed shrubs with defoliate trunks, including inflorescence 5- 12(-20) dm tall, the densely leafy, simple or few-branched homotinous stems terminating in a simple efoliate pseudoraceme of dense globose capitula exserted 1-4 dm from foliage, the stems, lf-stks and axes of inflorescence either densely hispid with erect-incurved setae or densely strigose with forwardly appressed ones, the setae in either case at least proximally scaberulous, pallid or rufescent and to 0.6-2 mm, mixed with fine short puberulence, the subconcolorous lfts either finely puberulent on both faces, or sometimes glabrate ventrally, or glabrous on both faces, their forwardly setose-ciliate margin continuously pallid but not comeous-rimmed. Stipules firm erect lanceolate 3-10 x 0.6-2 mm, densely pubescent dorsally like stem, puberulent within, persistent. Leaf-stalks 2-15 cm, the petiole 0.5-4.5 cm x 7-1.5 mm, the longer interpinnal segments 3-11 (—15) mm; pinnae 4-13-jug., subequilong or a little decrescent at each end of lf-stk, the rachis of longer ones (1.2-) 1.5-5 cm, the interfoliolar segments 0.4-1.5 mm; lfts of longer pinnae 15-36-jug., subequilong except at very ends of rachis, the blades narrowly lance-oblong, obliquely elliptic, or semi-ovate from semicordate base, at apex acute or apiculate, those near mid-rachis 3-7 x 1.1-2 mm, 2.2—4.7 times as long as wide, all weakly (2-)3(-4)-nerved from pulvinule, the simple midrib displaced to divide blade ±1:2, the inner posterior nerve expiring near or beyond mid-blade, the exterior 1 or 2 much shorter, none branched, the venation either immersed and discolored, or bluntly prominulous on one or both faces. Peduncles 1-3 per node 4-16 mm; capitula without filaments 5-8 mm diam., prior to anthesis moriform, the fl-buds gray-puberulent; receptacle setose; bracts narrowly lance-elliptic or linear-oblanceolate 1.5-3.3 x 0.2-0.5 mm, near apex dorsally puberulent and setose-ciliolate; flowers 4-merous 4-androus, all or almost all bisexual; calyx paleaceous-pappiform 1.7-2.9 mm, the lobes decompound almost or quite to base into lustrous setae; corolla subtubular 2.5-3.2 mm, the concave but not much thickened lobes 0.7-0.85 x 0.4-0.5 mm, gray-puberulent externally; filaments pink, free to base, exserted 4-4.5 mm; anthers 0.35—0.4 mm diam.; style about as long as filaments. Pods numerous in each capitulum, sessile, obliquely obovate in profile, at apex broadly rounded or obliquely subtruncate, compressed but turgid, 4.5-10 x (3.5-)4-7 mm(l-)2- seeded, the replum at broadest 0.5-1 mm wide, at maturity breaking apart at apex, the stiffly papery brown valves then basipetally dehiscent in one piece and gaping to release the seeds, remaining attached only at base, the cavity divided between the two ovules by a hyaline septum, the replum and valves alike densely hispid or less often strigose with basally dilated setae 0.5-3 mm; seeds (of var. regnellii, of the rest not seen) plumply obovoid ±3.5 x 2.5 mm, the testa dull chocolate-brown.

Bentham’s concept of M. regnellii, of necessity narrow because based exclusively on Regnell’s plants from Caldas, is here materially enlarged southward to incorporate M. supersetosa Burkart and allied forms from Paraná and Sta. Catarina. When Burkart described M. supersetosa he compared it, not with true M. regnellii, which he knew primarily from description and from the plate in Flora brasiliensis, but with the then undescribed M. deceptrix, equivalent to the species that passes in Flora ilustrada catarinense as M. regnellii. From M. deceptrix Burkart’s new species is easily and properly distinguished, but from genuine M. regnellii it differs only in smaller, more condensed leaves, which lend it, however, a certain distinction of mien that coincides with extratropical dispersal. The type-collections of M. regnellii have linear-oblong leaflets proportionately narrower than those of M. supersetosa, but Sa. de Caldas later yielded (Mosén 1966, S) leaflets of semi-ovate type. As flowers and pods of M. regnellii and M. supersetosa are nearly identical it is no longer possible to maintain them as independent species.

In eastern Paraná M. regnellii is subject to variation in indumentum and leaf-formula that appears related to dispersal and prompts me to distinguish, in addition to var. supersetosa, a glabrate var. exuta found in highland campo north and west of Curitiba, and from the neighborhood of Ponta Grossa a var. grossiseta, different in the coarsely dilated setae of leaf-stalks and in pod strigose with short bulbous-based setae.