Fig. 10.

The endothelium. (A) Longitudinal section of two neighbouring endothelial cells carrying labyrinthine wall. The radial wall between them is thinner towards the inner parenchyma. (B) Longitudinal section through the micropyle, showing the filling substance (white asterisk) near an endothelial cell (Et). (C) Fluorescence light micrograph of the endothelium after calcofluor white staining, showing the labyrinthine wall complex under UV light excitation. (D) Electron micrograph of portion of a cross-section in the endothelium, showing the continuity of wall protuberances on both sides of the thin radial wall between adjacent endothelial cells. Abbreviations: Et, endothelium; IP, inner parenchyma cell; LW, labyrinthine wall.