Markg., Ann. Missouri Bot. Gard. 52:385.1965
Dioecious liana, glabrous, highly ramified, contorted, widely spreading (usually in a single large tree), to more than 30 m in canopy; trunk 15-20 cm diam near ground, coarse, unfissured, the nodes enlarged. Leaves opposite, decussate; petioles 5-12 mm long, canaliculate above; blades narrowly to broadly ovate, acute to shorta-cuminate, acute to rounded at base, 9-15 cm long, 4-10 cm wide, ± thick, the midrib usually ± arched, the margin weakly revolute. Staminate inflorescences axillary and terminal, l- or 2-branched, the main axis of 1-4 tiers, each 1-4 cm long and terminated by 2 small, opposite, acute, connate bracts subtending a dense cluster of moniliform trichomes, a whorl of 2-9 simple strobili, and the axis of the next higher tier; side branches of 1 or 2 tiers identical to those of the main axis; staminate strobili greenish-brown, 10-18 mm long and 3 mm wide, their stalks slender, 5-10 mm long; staminate flowers numerous, in 6 or 7 whorls, 1-2.5 mm apart (uppermost whorl of a few, usually sterile, pistillate flowers, interspersed in a dense mat of white moniliform trichomes 1.5-1.8 mm long); each whorl of staminate flowers on the strobilus subtended by a collar of circular bracts, these at first cup-shaped, becoming saucer-shaped; staminate perianth obconic, brownish, angulate, 0.8 mm long and 0.3 mm wide; stamen solitary, 1.2 mm long, with 2 unilocular microsporangia. Pistillate inflorescences smaller and more reduced than staminate; strobili simple or 1-branched, the main axis of 3-5 tiers, each terminated by 2 opposite, acute, connate bracts subtending the axis of the next higher tier and a whorl of 5 pistillate flowers embedded in a dense cluster of moniliform trichomes; pistillate flowers brownish-yellow, subglobose, 0.5 mm wide and high, ovule 1 (most soon abort). Fruiting internodes 5-30 mm long, ca 2 mm wide, the nodes swollen; mature seeds oblong, 4.5-5 cm long and ca 2 cm wide, rounded on ends (apex apiculate on drying); external envelope red-orange becoming violet-purple, smooth, leathery, 2 mm thick; inner envelope brown, thin, faintly veined. Croat 7958.
Infrequent, in the forest. The species appears to flower twice per season, principally from February to April and at least sometimes again in August or September. The fruits from the dry-season flowering develop to mature size by July or August, whereas the wet-season flowers produce fruits in the early dry season. Foster (pers. comm.) reports that the plants flowering during August and September are not the same individuals as those that flowered in the dry season. However, there are indications that individuals may flower twice per year, since I have observed plants in April with both flowers and fruits. Because it is unlikely that the fruits persisted on the plant all year, they were probably the result of a second flowering. Foster also observed an individual, seen bearing fruits in July and August 1971, with mature-sized green fruits in January 1973. This indicates that if individual plants flower only once a year, i.e., in dry or wet season, they are not necessarily restricted to that single period.
Fruits are probably mammal dispersed. Oppernheimer (1968) reported that white-faced monkeys probably feed on the fruits.
The typical variety of Gnetum leyboldii restricted to the Amazon basin, principally in Brazil, Colombia and Ecuador. The variety woodsonianum extends from Coclé in Panama to northern Colombia. In Panama, it is known principally from tropical moist forest in the Canal Zone, Coclé, and Darién, but also from Cerro Pirre in Darién, which ranges from tropical wet forest to premontane rain and lower montane rain forests.
See Figs. 41 and 42.