Mimosa pithecolobioides Benth.

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 pithecolobioides Benth.

Type

13. Mimosa pithecolobioides Bentham, Trans. Linn. Soc. London 30: 413. 1875 & in Martius, Fl. bras. 15(2): 357, descr. ampliat. 1876.- ". . . in Taboleira camporum provinciae Minas Geraes australioribus et prope Mariana: Martius."-Holotypus, collected II

Synonyms

Mimosa lasiophylla Benth., Mimosa pithecolobioides var. brachystachya Benth.

Description

Species Description - Unarmed, potentially arborescent shrubs and round-topped trees flowering when 2-5 m tall, variably pubescent either with short scattered subappressed hairs or with many erect gray hairs 0.2-0.5 mm, eglandular, the branchlets obtusan- gulate, the ample venulose lfts bicolored, when dry lustrous dark brown and either glabrous or minutely puberulent above, beneath paler, dull-rufous and either glabrous or pilosulous, the sub-virgate or pyramidal panicle of short dense amentiform fl-spikes leafless or vestigially leafy proximally and exserted 1-3 dm from foliage, but its branchlets subtended by rudimentary lf-stks each with a concave nectary. Stipules narrowly lanceolate or subulate 1.5-4.5 mm, at base 0.3-0.9 mm, subpersistent. Leaf-stalk of major lvs 2.5-8.5 cm, the petiole including obese hard pulvinus 4-8 mm, the longer (sometimes single) interpinnal segments 11-26 mm, the rachis openly grooved ventrally, spicules 0; a round or vertically elongate concave nectary 0.9-2.3 mm diam. between first pair of pinnae, smaller ones sometimes between succeeding pairs, and less often also between some pairs of lfts; pinnae 2-5-, commonly either 2-3- or 2—4-jug., decrescent proximally, the rachis of distal pair 4-7 cm, its longer interfoliolar segments 10-21 mm; minute (deciduous) subulate paraphyllidia 0.1-0.45 mm next to pulvinus of each pinna; lfts of distal pair of pinnae 3-6-, usually 4- or 5-, exceptionally 5-8-jug., accrescent distally, the terminal pair largest, the blade of these obliquely obovate or elliptic-obovate, obtuse or shallowly emarginate, minutely apiculate, (15-)20-55 x (10-) 16-33 mm, at base shallowly asymmetrically cordate, marginally revolute, the subcentric, straight or forwardly curved midrib giving rise on each side to 2-3 major (and sometimes intercalated minor) secondary nerves brochidodrome well within the margin, these and an open tertiary venulation prominulous on both faces of blade but more sharply so beneath. Flowerspikes including short peduncle 1.5-3 cm, without filaments 4-5 mm diam., the fls at anthesis subcontiguous, the amentiform immature ones grayish-puberulent; peduncular bracts ovate or lance-elliptic 0.6-1.5 mm; floral bracts submembranous 0.3-0.5 mm, persistent; flowers 5-merous 10-androus, some or many of each spike functionally staminate; calyx campanulate (0.6-)0.7-1.2 mm, pilosulous, the broadly triangular or deltate teeth 0.2-0.4 mm; corolla (1.7-)2-2.5 mm, its erect, narrowly ovate subacute, strongly 1-nerved lobes (0.5-)0.7-l x 0.3-0.45 mm, pilosulous externally; filaments cream-colored, the longer ones exserted 1.8—3(—3.5) mm; anther-connective produced beyond thecae as a minute point; ovary subsessile, at anthesis glabrous or rarely puberulent. Pods subsessile, in profile narrowly oblong ±50-100 x 11-15 mm, piano-compressed, cuneate at base and abruptly cuspidate at apex, the shallowly undulate rimlike replum ±0.8 mm diam., the papery, glabrous or pilosulous valves separating when ripe from replum and breaking up into 5-8 rectangular free-falling indehiscent articles 10-13 mm long; seeds plumply discoid 4.5-5 mm diam., the testa castaneous dull.

Distribution and Ecology - In cerrado and campo rupestre, 775-1200 m, scattered along both slopes of s. Chapada Diamantina and Sa. do Espinhaço in lat. 14°-21°S, from Sa. Geral de Caitité in s.-centr. Bahia to Ouro Preto in s.-centr. Minas Gerais, and collected once in early days near Ytú in s.-w. S. Paulo.—Fl. (I-)II-IV. Map 3.

Discussion

Within its range and environment M. pithecolobioides is the only mimosa that has petiolar nectaries and spicate flowers. Within ser. Glanduliferae a lack of prickles and a free-standing, fruticose or arborescent growth-form are notable specific characters plausibly correlated with adaptation to cerrado and campo rupestre habitats. The only other spicate Glanduliferae are prickly lianas, M. lawranceana of the northern Colombian Andes, and a rare and abnormal form of M. rufescens known only from Pará. The species nearest to M. pithecolobioides is the also freestanding and almost unarmed M. irrigua, endemic to the heights of Chapada Diamantina in north-central Bahia; but this has the petiolar nectary near mid-petiole and flowers in globose capitula.

Mimosa pithecolobioides is conspicuously variable in pubescence of stems and foliage. The glabrate state, corresponding to the species as originally described and including the negligible var. brachystachya, is now known from the northern and southern points of the whole species-range and randomly between them. The villosulous state appears dominant in north-central Minas Gerais, but not to the exclusion of the glabrate one. The plants are otherwise identical, and there seems no advantage to be had from perpetuating a taxonomic distinction between them. The manuscript epithet lasiogynum applied by Martius to the type of M. pithecolobioides was a misnomer, the ovary at anthesis being completely glabrous.

Distribution

Brazil South America| Bahia Brazil South America| São Paulo Brazil South America| Minas Gerais Brazil South America|