Pourouma
Description
Trees, terrestrial, often with stilt-roots; internodes solid. Scars of the stipules transverse; blade basally attached, palmately incised or entire, venation pinnate to sub palmate. Inflorescences branched (or unbranched and subumbellate), with the flowers ± disperse or (in staminate inflorescences) in terminal, globose heads, ebracteate or sometimes bracteate. Tepals of the staminate flowers (3 or) 4, free or connate; stamens (3 or) 4, free. Perianth of the pistillate flower tubular; stigma (sub)peltate or knob-like. Fruit large (1-2 cm long), dry, enclosed by the enlarged, fleshy perianth, the outer layer of which turning black(ish) at maturity, fruit and perianth constitute a "pseudodrupe", endosperm absent; cotyledons thick.
Distribution
Guianas present, Neotropics present
Neotropics 26 species; in the Guianas 10 species known and P. bolivarensis expected.
Wood
Vessels diffuse, solitary (55-95%) and in radial multiples and irregular clusters of 2-3, round to oval, 1-6 per sq. mm, diameter 125-255 μm. Vessel-member length: 475-850 μm. Perforations simple. Intervascular pits alternate, round or polygonal, 10-20 μm. Vessel-ray and vessel- parenchyma pits larger, often elongated, half-bordered. Thin-walled tyloses present or absent.
Rays uniseriate and 2-5-seriate, 4-9 per mm, up to 450-1280 μm high. Heterogeneous, composed of procumbent, square and upright cells, with uniseriate margins of 1-6 rows, occasionally vertically compound. Rhom- bic crystals sometimes present. Radial latex tubes observed inP. melinonii .
Parenchyma paratracheal, variable, vasicentric and aliform to confluent and even banded. Bands regular, wavy, 2-3 per mm, sometimes apotracheal terminal bands. Strands of 5-6 cells. Rhombic crystals common.
Fibres non-septate, lumen 18-36 μm, walls 1-4 μm. Pits simple, small, mainly on the radial walls. Gelatinous fibres present or absent. Length: 940-1725 μm. F/V ratio: 1.6-2.7.
Rays uniseriate and 2-5-seriate, 4-9 per mm, up to 450-1280 μm high. Heterogeneous, composed of procumbent, square and upright cells, with uniseriate margins of 1-6 rows, occasionally vertically compound. Rhom- bic crystals sometimes present. Radial latex tubes observed in
Parenchyma paratracheal, variable, vasicentric and aliform to confluent and even banded. Bands regular, wavy, 2-3 per mm, sometimes apotracheal terminal bands. Strands of 5-6 cells. Rhombic crystals common.
Fibres non-septate, lumen 18-36 μm, walls 1-4 μm. Pits simple, small, mainly on the radial walls. Gelatinous fibres present or absent. Length: 940-1725 μm. F/V ratio: 1.6-2.7.