Pristimera
Description
Lianas or small shrubs with scandent branches, glabrous throughout; branches opposite, lenticellate. Leaves with tertiary veins orthogonally reticulate, prominulous on both surfaces, often yellowish. Inflorescences axillary, generally densely flowered, corymbose, (pseudo-) dichotomously branched; bracts and bracteoles small. Flowers small, 2-5 together at the end of the ultimate branchlets; sepals 5; petals 5, spreading or erect; disk very low, forming a round or slightly angular low cushion around the ovary, without or with a free upper margin; stamens 3, filaments deltoid, suberect or extrorsely reflexed, anthers transversely ellipsoid, dehiscing by extrorse, transverse, confluent clefts; ovary depressed-trigonous, 3-lobed, ovules 2-10 per locule, superposed, style short, ending in a stigmatic shield or with 3 minute stigmas. Infructescences with several fruits. Fruits capsular, with 3, divergent, erect mericarps, separately attached to a hardly swollen receptacle. Mericarps flattened on both surfaces, dehiscing along an unobtrusive median suture, pericarp thin-coriaceous; seeds erect from the base, affixed by a large, papery, basal wing, embryoniferous part as long as or shorter than the wing, leathery.
Distribution
C America present, Guianas present, N Argentina present, Neotropics present, Pantropical present, S Brazil present, Southern America: Paraguay (Paraguay present)
Pantropical, 24 species, 9 of which in the Neotropics, from C America and the West Indies south to S Brazil, Paraguay and N Argentina; 5 species in the Guianas.
Wood observation species
Wood
Growth rings present, border due to a narrow layer of radially com- pressed fibres, a dilatation of the wide rays, and presence of non-ligni- fied zones in the wide rays.
Vessels diffuse, mostly solitary but some radial multiples of 2 often present (not inP. nervosa ), usually 20-40(15-100) per sq. mm, round to oval, of two different sizes, narrow vessels 20-30 μm wide, wide vessels 100-160(180) μm in diameter. Vessel-member length: 545 (400-700) μm. Perforations simple. Intervascular pits alternate, elong- ate, with enclosed slits, 4-8 μm, mostly 5 μm. Vessel-ray pits often rare, similar to the intervascular pits, and occasionally with confluent slits giving a striate appearance.
Rays uni-and multiseriate, the uniseriates usually very scarce (more numerous inP. nervosa ), 4-6 per mm, the multiseriates 20-36 cells wide (150-500 μm). Heterogeneous, the body of the wide rays of irregular procumbent and square cells, few upright cells, up to 500 cells (=1 cm) and more high; the uniseriates usually not over 4 cells high, the cells upright. In the wide rays zones, usually V-shaped, of cells with unlignified walls occur at the growth rings borders. Rhombic crystals present, numerous, often most numerous in the marginal cells of the wide rays.
Parenchyma paratracheal, scanty vasicentric. Strands of 4-8 cells. Ground tissue of fibre-tracheids and septate fibres, intermingled, often the septate fibres rather scarce. Fibre-tracheids lumen 10-15 μm, walls 3-4 μm, small bordered pits numerous on both radial and tangential walls. Septate fibres difficult to observe, lumen slightly larger, walls c. 2 μm. Pits with minute borders on both radial and tangential walls. Length of septate fibres: 550(480-640) μm, of fibre-tracheids: 825 (777-844) μm. FIV ratio: 1.26-1.90.
Vessels diffuse, mostly solitary but some radial multiples of 2 often present (not in
Rays uni-and multiseriate, the uniseriates usually very scarce (more numerous in
Parenchyma paratracheal, scanty vasicentric. Strands of 4-8 cells. Ground tissue of fibre-tracheids and septate fibres, intermingled, often the septate fibres rather scarce. Fibre-tracheids lumen 10-15 μm, walls 3-4 μm, small bordered pits numerous on both radial and tangential walls. Septate fibres difficult to observe, lumen slightly larger, walls c. 2 μm. Pits with minute borders on both radial and tangential walls. Length of septate fibres: 550(480-640) μm, of fibre-tracheids: 825 (777-844) μm. FIV ratio: 1.26-1.90.