Fig. 1.

Foam-like cells and puzzle-like cells. Biological tissues, such as Drosophila epithelium (A), can adopt geometric resemblance to non-biological materials such as ‘artificial tissue’ in which surface tension processes dominate (B), here formed by coloured droplets of a solution diffusing in a less dense solution of the same salt (Fig. 180, p. 501, Thompson, 1942). (C) Cells presenting sinuous outlines (Fig. 186, p. 507, Thompson, 1942): endothelium of a blood-vessel (a); and plant tissues Impatiens (b) and Festuca (c). (D) Confocal image of the PCs in mature Arabidopsis leaves that have grown into jigsaw piece-like shapes. Scale bars: 10 µm in A; 50 µm in D.