Monographs Details: Macrolobium palustre Ducke
Authority: Cowan, Richard S. 1953. A taxonomic revision of the genus Macrolobium (Leguminosae-Caesalpinioideae). Mem. New York Bot. Gard. 8 (1): 257-342.
Family:Caesalpiniaceae
Description:Distribution and Ecology - Small tree, the branchlets glabrous. Leaves unijugate to bijugate; the petioles 13-18 mm. long, canaliculate; rachis 0-22 mm. long, canaliculate, glabrous. Leaflets 6.5-9.5 cm. long, 3-4 cm. wide, glabrous, epunctate, slightly arcuate, elliptic, the base inequilateral, acute, the apex acute with a rounded-truncate extremity; costa subimpressed on the upper surface, salient beneath, the venules prominent. Inflorescences to 7 cm. long, glabrous, the peduncles 5-6 mm. long; pedicels 6-8 mm. long, glabrous; bracteoles 10-11 mm. long, 5 mm. wide, oblong and cuspidate or elliptic and acute, glabrous, coriaceous. Hypanthium 2 mm. long on a stipe about 1 mm. long, glabrous. Sepals four, 7-8 mm. long, 2.5-3 mm. wide, lanceolate or oblong-lanceolate, acute, slightly concave, ciliolate in the apical portion. Petal blade 6 mm. long, 7.5 mm. wide, transversely oval, the claw 5-6 mm. long, a uric u late basally, glabrous externally, ciliolate on the lower portion of the claw, villose within on the claw and up to the center of the blade. Filaments 16.5 mm. long, villose basally. Stigma capitate. Style 13 mm. long, glabrous. Ovary 2.5 mm. long, 1.5 mm. wide, oblong, glabrous, 1-2-ovulate, the gynophore 2.5-3 mm. long, glabrous, inserted midway on the adaxial hypanthial wall. Fruit unknown.

Discussion:

Figure 11.

Type Collection: A. Ducke (H.J.B.R. No.) 35193, "Igarape Macacury, Rio Negro, Cucuhy," Amazonas, Brazil, September 1935 (HOLOTYPE RB, isotypes G, P, U, US).

Macrolobium palustre is obviously related to M. pendulum but differs in so many characters, both quantitative and qualitative, that it has been regarded as specifically distinct, although the first reaction was to treat it as a variety within (A.pendulum. In addition to differing by the frequent occurrence of bijugate leaves, M. palustre has caducous stipules, longer petioles, longer sepals and petal claw, and basally villose filaments. Also, whereas M. pendulum is distributed along the lower basin of the Amazon River, this species is known only from the upper Rio Negro region.