Notes on the Systematic Anatomy of Whittonia and Peridiscus

Abstract

Adaxial epidermis with markedly sinuous anticlinal walls; stomata absent. Abaxial epidermis with abundant, dome-shaped papillae with somewhat thickened apices, there usually being one such papilla to each epidermal cell. Large, 4-sided to polygonal crystals present in cells adjacent to the vascular bundles, more often visible from the adaxial than from the abaxial side of the leaf. Individual crystals sometimes concentrically zoned, or with a transverse fissure giving each crystal a paired appearance. Occasional crystals present in crystal-idioblasts in the epidermis itself. Stomata anomocytic with crescent-shaped guard cells. Lamina exhibiting a dorsiventral mesophyll with a single adaxial layer of well marked palisade cells. Vascular bundles strongly supported by sclerenchyma which is usually vertically transcurrent. Midrib, projecting prominently from the abaxial surface of the lamina, and, in transverse section, exhibiting a large, cylindrical vascular strand, with the xylem much thicker in the adaxial and abaxial sectors than laterally, a wide, horizontally flattened, accessory, collateral vascular strand being present in the centre of the midrib. Petiole, in transverse sections through the distal end, with 2 cylindrical vascular strands, the more adaxial member of the pair being circular in outline and rather smaller than the slightly triangular abaxial strand. Vessels in the petiole xylem mostly in radial multiples.