Peritassa
Description
Lianas or shrubs with scandent branches; branchlets cinereous, sometimes minutely puberulous. Inflorescences axillary or arising from defoliate branches, thyrsoid-paniculate or corymbose or cymose, branches (pseudo-)dichotomously divided, glabrous or puberulent. Sepals 5; petals 5, weakly or distinctly erosulous; disk short-tubularwith sinuate margin; stamens 3, erect, anthers: thecae parallel or slightly divergent, vertically dehiscent, connective produced beyond the thecae or not; ovary subglobose, ovules 2 or 4 per locule, style short, truncate, stigmas inconspicuous. Fruits drupaceous, small or medium-sized, pericarp leathery, pruinose; seeds embedded in mucilaginous pulp.
Distribution
Guianas present, Southern America: Panamá (Panamá present), southern Brazil present
About 13 species from Panama to southern Brazil including the West Indies, 3 of which occur in the Guianas.
Wood
Growth rings absent or faint.
Vessels diffuse, solitary and very few radial multiples of2-3, 7-20 (up to 30) per sq. mm, round to oval, diameter of two sizes, the smallest 10-40 μm wide, the larger ones 80-100(-150) μm wide. Vessel-member length: 600(350-830) μm. Perforations simple. Intervascular pits alternate, 3-4 mm. Vessel-ray pits as the intervascular pitting. Sometimes vessels occluded by stone cells.
Rays exclusively uniseriate, very numerous, 20-26 per mm, hete- rogeneous, mostly square and upright cells, procumbent cells few or entirely absent. Height variable, usually c. 25 cells (0.5-0.7 mm), but in the species without included phloem often up to 40 cells (2-3 mm). Rhombic crystals frequent, in inflated cells or in divided ray cells. Parenchyma paratracheal, extremely scarce, restricted to an occasional strand bordering a vessel. Strands of 4-12 cells.
Ground tissue of fibre-tracheids and septate and non-septate fibres. Fibre-tracheids lumen 6-10 μm, walls 4-6 μm, small bordered pits on both radial and tangential walls. Fibres of both types with a lumen of 12-15 μm, walls 1.5-2.5 μm, pits simple, restricted to radial walls; septate fibres arranged in concentric bands or aliform-confluent in species without included phloem, if included phloem is present, distri- buted irregularly in patches between the vessels. Length fibre-tra- cheids: 800(756-830) μm. F/V ratio: 1.42(1.23-1.80).
Included phloem in concentric c. 1 mm wide bands, without stone cells, but with silica in some cells; without radial connections between rings (in the Guianan species).
Vessels diffuse, solitary and very few radial multiples of2-3, 7-20 (up to 30) per sq. mm, round to oval, diameter of two sizes, the smallest 10-40 μm wide, the larger ones 80-100(-150) μm wide. Vessel-member length: 600(350-830) μm. Perforations simple. Intervascular pits alternate, 3-4 mm. Vessel-ray pits as the intervascular pitting. Sometimes vessels occluded by stone cells.
Rays exclusively uniseriate, very numerous, 20-26 per mm, hete- rogeneous, mostly square and upright cells, procumbent cells few or entirely absent. Height variable, usually c. 25 cells (0.5-0.7 mm), but in the species without included phloem often up to 40 cells (2-3 mm). Rhombic crystals frequent, in inflated cells or in divided ray cells. Parenchyma paratracheal, extremely scarce, restricted to an occasional strand bordering a vessel. Strands of 4-12 cells.
Ground tissue of fibre-tracheids and septate and non-septate fibres. Fibre-tracheids lumen 6-10 μm, walls 4-6 μm, small bordered pits on both radial and tangential walls. Fibres of both types with a lumen of 12-15 μm, walls 1.5-2.5 μm, pits simple, restricted to radial walls; septate fibres arranged in concentric bands or aliform-confluent in species without included phloem, if included phloem is present, distri- buted irregularly in patches between the vessels. Length fibre-tra- cheids: 800(756-830) μm. F/V ratio: 1.42(1.23-1.80).
Included phloem in concentric c. 1 mm wide bands, without stone cells, but with silica in some cells; without radial connections between rings (in the Guianan species).