Fig. 10.

Summary diagrams of stomatal development in (A) Ephedra, (B) Gnetum and (C) Welwitschia, with photomicrographs in the right-hand column. In the diagrams cells are coloured/textured as follows: green, meristemoid or guard mother cell; dark grey, perigene lateral subsidiary cell (LSC); blue, first mesogene LSC; yellow, second mesogene LSC; red, guard cell. In (A) both LSCs are perigene. In (B) and (C) the stomatal meristemoid divides twice and passes through a distinct triad stage before achieving the full complement of four cells in the stomatal complex. In Gnetum (B) the LSCs themselves often undergo secondary mitosis, but further LSC division does not occur in Welwitschia (C).