Macrosamanea amplissima (Ducke) Barneby & J.W.Grimes

Authors

Rupert C. Barneby

Authority

Barneby, Rupert C. & Grimes, James W. 1996. Silk tree, guanacaste, monkey's earring: a generic system for the synandrous Mimosaceae of the Americas. Part I. Abarema, Albizia, and allies. Mem. New York Bot. Gard. 74: 1-292.

Family

Mimosaceae

Scientific Name

Macrosamanea amplissima (Ducke) Barneby & J.W.Grimes

Type

". . . in silva a Rio Negro periodice inundabile prope Cucuhy (civ. Amazonas [±1°N, 67°W]), 21-9-1935 leg. A. Ducke H[erb]. J[ard]. B[ot]. R[io de Janeiro] 35527." — Holotypus, RB (2 sheets)!; isotypus, US 1740710!

Description

Species Description - Coarsely macrophyllidious weak trees and bush- ropes attaining 5-15 m, with obtusely 4-angular woody branches, either glabrous below the inflorescences or the young branchlets and lf-axes minutely thinly puberulent, the ample subcoriaceous lfts bicolored, lustrously olivaceous above, paler (when dry brunnescent) beneath, the dense capituliform racemes of ascending, very long and narrow fls either solitary or paired in the axil of a few distal, coeval or lately fallen lvs, the pedicels, calyces, and corollas all densely minutely furfuraceous-puberulent with sordid or gray hairs. Stipules (few seen) thick-textured, triangular 1-1.5 mm, either persistent or deciduous. Lf- formula (iv-)v-vii/(9-)10-14; lf-stks 2.5-6 cm, subterete, the petiole including coarsely wrinkled pulvinus 3-10 cm, at middle 4-6 mm diam, the longer interpinnal segments 7-10 cm; first nectary situated next to lf-pulvinus, sessile, patelliform, or buttonshaped 4-6 mm diam, similar but progressively smaller ones between each pair of pinnae and between or immediately below each pair of lfts, the latter sometimes incipiently stalked; pinnae a little decrescent at each end of lf-stk, the rachis of longest ones 1.5-2.6 cm, the longer interfoliolar segments (13-) 17-24 mm; pulvinules transversely linear- elliptic 0.5-0.7 x 2-3 mm; lfts a little decrescent proximally, the first pair arising 3-7 mm distant from minute conic caducous paraphyllidia (one of these exceptionally dilated into a diminutive 1ft), the blades, except for the always larger, obliquely rhombic-elliptic distal pair, subequiform, exactly or subfalcately rhombic from inequilaterally cuneate base, obtusangulate but often minutely mucronulate at apex, those near and above midrachis 30-65 x 13-25 mm, 2.2-2.6 times as long as wide; costa diagonal, gently or obscurely sigmoid, giving rise on each side to ±8-12 major secondary nerves brochidodrome shortly within the revolute margin, these and some weak and irregular tertiary venules finely prominulous on both faces but more sharply so beneath. Peduncles stout 1.5-5.5 cm, bearing at apex ±3-4 deltate reflexed bracts charged ventrally with a homy patelliform nectary; fls ±36-60 per capitulum, crowded on a deeply pitted and wrinkled receptacle 8-25 x 4-7 mm; floral bracts dimorphic, the lower ones deltate-ovate or oblance-spatulate, early dry caducous, the upper ones resembling bracts of peduncle though smaller, reflexed deltate persistent, charged ventrally with a small plane nectary; pedicels 3.5-8 mm; calyx cylindric, distally dilated, 13-18 mm, at middle 2-3.5 mm diam, the ovate deltate lobes 2.5-3 mm; corolla slenderly trumpet-shaped 40-53 mm, the lanceolate lobes 3.5-7 mm; androecium ±110-150-merous but many shorter stamens sterile, the longest 6.5-8.5 cm, the tube adnate to corolla through ±5-10 mm, either as long as or to 10 mm longer than it; style exserted beyond longer stamens, the dilated tip 0.2 mm diam. Pods usually solitary, subsessile, oblong or broadly linear in profile, rounded at both ends but excentrically apiculate, (12-) 14-26 x 5.5-7 cm, the leathery brown valves at first plane, framed by the narrowly elevated sutures, tumescent as the seeds swell, transversely venose, minutely puberulent overall but glabrate in age; dehiscence through the length of both sutures, the valves narrowly gaping to release the seeds; funicle filiform; seeds 10-16 per pod, transverse at middle of the valves, narrowly imbricate lengthwise, plumply discoid, in broad profile broad-elliptic and 29-34 x 21-24 mm, the lustrous castaneous, membranous and brittle testa crumpled facially, girdled by a prominent dark nerve.

Distribution and Ecology - A bush-rope in dense forest, becoming independently treelike in more open places, scattered in lowland terra firme forest and in igapó at ±90-250 m within the NW quarter of the Amazon basin: in E Vaupés, Colombia (ríos Vaupés and Apoporís); in T. F. Amazonas, Venezuela (ríos Guainía-Negro); and in state of Amazonas, Brazil (Río Negro and immediate affluents downstream to Río Cueiras; middle Río Madeira). — Map 52. — Fl. VII-IX(-?); fr. V, IX-X, apparently maturing slowly over several months.

Discussion

The aptly named Macrosamanea amplissima is distinguished in its genus by coarse leaves, ample coriaceous leaflets, broad tumid pod, pedicellate flowers crowded along a clavate receptacle and thus technically racemose, and by the nectary on the bract subtending some flowers as well as on the sterile bracts at base of the capitulum. The foliage of M. duckei is sometimes similar, but its flowers are both sessile and much shorter.

Distribution

Vaupés Colombia South America| Amazonas Venezuela South America| Amazonas Brazil South America|