Urera
Content
Description
Tree(lets) shrubs or subshrubs, usually dioecious, (usually) with stinging hairs or prickles. Leaves in spirals (to distichous); stipules connate; blade pinnately veined. Inflorescences paniculate, dichotomously or more or less irregularly branched, with the flowers solitary or in glomerules; flowers pedicellate or sessile. Staminate flowers with 4-5, basally connate tepals; stamens 4-5. Pistillate flowers with 4, equal or unequal, basally connate tepals; stigma penicillate-capitate, persistent on the hooked apex of the fruit. Achene partly enveloped by a slightly enlarged, juicy perianth.
Distribution
Africa present, Guianas present, Neotropics present present
Mainly in Africa and the Neotropics approx. 20 species; in the Neotropics 5-8 species; in the Guianas 3 species.
Wood
Growth rings absent. Vessels diffuse, mainly solitary and sometimes in clusters of 2-4, round to oval, 2-8 per sq. mm, diameter 100-180 μm. Vessel-member length: 180-270 μm. Perforations simple. Intervascular pits alternate, polygonal, 9-18 μm. Vessel-ray and vessel-parenchyma pits as the intervascular pits. Thin-walled tyloses present or absent.
Rays only 2-4-seriate (= 40-50 μm), 1-3 per mm, up to several mm high. Heterogeneous, composed of square and upright cells, sometimes partly unlignified. Sheath cells common. Druses sometimes present.
Parenchyma paratracheal vasicentric. Strands of 2-4 cells. Apotracheal parenchyma mainly unlignified, occuring as islands or bands in transverse sections, containing druses, often storied.
Fibres non-septate, lumen 12-24 μm, walls 3-6 μm, often storied. Pits simple, on radial and tangential walls. Length: 825-1255 μm.
Rays only 2-4-seriate (= 40-50 μm), 1-3 per mm, up to several mm high. Heterogeneous, composed of square and upright cells, sometimes partly unlignified. Sheath cells common. Druses sometimes present.
Parenchyma paratracheal vasicentric. Strands of 2-4 cells. Apotracheal parenchyma mainly unlignified, occuring as islands or bands in transverse sections, containing druses, often storied.
Fibres non-septate, lumen 12-24 μm, walls 3-6 μm, often storied. Pits simple, on radial and tangential walls. Length: 825-1255 μm.