Pleurisanthes

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Pleurisanthes

Description

Lianas or scandent shrubs. Stems and older branches flattened or strap-shaped, young branches terete. Leaves with conspicuous prominent reticulated venation. Inflorescences axillary, supra-axillary or terminal panicles or, single or clustered and sometimes spiciform racemes, often with flattened rhachis. Flowers small, perfect, (sub-) sessile or pedicellate, without articulation on pedicel, often arranged in clusters on one side of rhachis; calyx cupulate, 5-lobed, densely strigose outside, glabrous inside; petals 4-5, free or agglutinated at base, white or cream, fleshy, apex inflexed, midrib frequently prominent, strigose outside, glabrous inside; stamens 4-5, free, glabrous, filaments filiform, anthers-rounded to oblong, longitudinally dehiscent; ovary conical, pilose, 1-celledwith 2 collateral ovules, style minute to well developed. Fruit a drupe.

Distribution

Guianas: present present Southern America:
6 species in the Guianas and Brazil; 4 of which in the Guianas.

Wood observation species

P. jlava

Wood

Vessels 'diffuse', solitary and few clusters of 2-3, round to oval, 9(8-11) per sq. mm, diameter 170-250 μm. Vessel-member length: 413(265-529) μm. Perforations simple. Intervascular pits alternate, round or polygonal, 7-12 μm. Vessel-ray and vessel-parenchyma pits similar to the intervascular pits, or slightly larger(= elongated), sometimes unilaterally compound.
Rays in two types, 4-5 per mm, uni-biseriate, over 750 μm (= 14 cells) high, heterogeneous, composed of square, upright and some pro- cumbent cells; and multiseriate, 5-7 cells wide, over 3000 μm (= 150 cells) high, heterogeneous, composed of square, upright and procumbent cells; sometimes with stone cells. Rhombic crystals present. Parenchyma paratracheal aliform(-confluent), and apotracheal diffuse and in one cell wide wavy and short tangential bands. Rhombic crystals present.
Fibres non-septate, lumen up to 10-15μm, walls up to 4-5 μm. Pits bordered, on radial and tangential walls, 4-5 μm. Length: 809(588- 1235) μm. F/V ratio: 1.96.
Included phloem present as concentric bands, however not circular as the stem developed only in two directions.