Monographs Details: Mimosa rheiptera 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.
Family:Mimosaceae
Scientific Name:Mimosa rheiptera Barneby
Synonyms:Mimosa foliolosa Benth., Mimosa claussenii Benth., Mimosa claussenii var. microphyllidia Barneby
Description:Species Description - Trees attaining 4 m, with slender homotinous branches clad in proportionately long narrow multipinnate microphyllidious lvs, the axis of stem, lf-stks and peduncles pilose with weak ascending setae to ±1.5 mm mixed with scattered villi and many small orange gland-tipped setulae, the lfts glabrous facially or thinly setulose beneath, sparsely gland-cioliolate, the inflorescence an open pseudoraceme projected at anthesis ± 1 dm from expanded foliage but hysteranthously foliate. Stipules firm ovate-acuminate ±4-5 x 2-3 mm, pubescent externally like stem, glabrous castaneous within, deciduous before the associated lf. Leaf-stalks ±12-19 cm, the petiole reduced almost to an obese hard pulvinus, the longer interpinnal segments 5-7 mm; spicules 0; pinnae ± 33-35-jug., markedly decrescent basipetally from near mid-lf, slightly so distally, the rachis of longer ones 25-31 mm, the longer interfoliolar segments 0.6-0.9 mm; lfts of longer pinnae 29-33-jug., the first pair next to pulvinus, the blades oblong obtuse, the largest 2.5-3.5 x 0.7-0.9 mm, all becoming 3-nerved beneath. Peduncles solitary and paired 5-8 cm; capitula subglobose, without filaments 13-14 mm diam., prior to anthesis conelike; bracts spatulate-oblanceolate ±4.5 mm, beyond middle densely setose and glandular-setulose dorsally; flowers 4-merous 8-androus, the staminate lower ones a little shorter than the rest; calyx-tube 0.6 mm glabrous, the undulate rim with a few plain or capitellate setulae 0.2-0.3 mm; bisexual corollas 5-6 mm, the lobes ± 1 mm, silvery-setulose dorsally; filaments pink, exserted to 17 mm; pod unknown.

Distribution and Ecology - In "grassland at edge of cerrado" and in gallery margin, 700-1000 m, known only from the municipios of Veadeiros and Cavalcante near 14°S in e.-centr. Goiás.—Fl. IV-V(-?).

Discussion:

This elegant but troublesome mimosa appears very closely related to M. claussenii var. microphyllidia, with which it shares slender arborescent stature and extended, hysteranthously foliate inflorescence; but its extremely short pinnae and tiny leaflets are more suggestive of M. foliolosa sensu lato. If referred either to M. claussenii or to M. foliolosa, it breaks down the already fragile distinction between these two already unwieldy complexes. Although I suspect that M. rheiptera represents an extreme microphyllidious expression of the M. claussenii line, I describe it as an independent species for taxonomic convenience. If the pod turns out to be that of M. claussenii, the status of M. rheiptera will need reassessment.

In general habit of growth M. rheiptera resembles M. struthionoptera, but the latter stands well apart, nevertheless, in dense velvety-villosulous indumentum, longer narrower stipules, and fewer pinnae accommodating to 45-50 (not ±30) pairs of leaflets. The wholly eglandular M. densa differs yet further in having leaves and compact inflorescence crowded at tip of decorticate branches and in smaller flowers with filaments hardly half as long.

Distribution:Brazil South America| Goiás Brazil South America|

Narratives:Mimosa rheiptera