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Herbs, dioecious or monoecious. Leaves opposite, those of a pair often unequal in size and shape; stipules connate; blade with pinnate, sub-triplinerved or single-nerved venation. Inflorescences unisexual or bisexual, branched or unbranched; flowers pedicellate or sessile. Staminate flowers with (3 or) 4, connate tepals; stamens (3 or) 4. Pistillate flowers with 3, basally connate, unequal tepals, the middle one the largest; stigma capitate-penicillate, persistent or caducous. Achene subtended by the hardly enlarged tepals.


Guianas present, Neotropics present, Pantropical present
Pantropical with more than 600 species; in the Neotropics more than 300 species; in the Guianas 4 species.


Growth rings faint or absent. Vessels diffuse, solitary and in radial multiples and irregular clusters of 2-4, round to oval, 24-40 per sq. mm, diameter 40-85 μm. Vessel-member length: 205-250 μm. Perforations simple. Intervascular pits alternate, round or polygonal, 6-9 μm, sometimes scalariform. Vessel-ray and vessel-parenchyma pits as the intervascular pits. Thin-walled tyloses present or absent.
Rays only multiseriate, 1-2 per mm, entirely composed of upright cells, up to several mm high. All rays to be classified as medullary rays. Parenchyma paratracheal, as vasicentric rings.
Fibres non-septate, lumen 9-15 μm, walls 3-5 μm. Pits simple, on radial and tangential walls. Length: 370-435 μm.


No material available from the Guianas. Based on Bonsen & ter Welle (1984): P. spec. (Equador).