Figure 4: Sporophyte of Fucus distichus 10 days after fertilization. (A) Overview of thallus. Beginning of differentiation of cell layers can be seen. (B) Outer and inner cell layers. N, nucleus. Rectangle indicates area of wall with pit field. (C) Enlarged image of pit field in cross wall between cells of outer layer (rectangle in B). (D) Pit fields in cell wall between outer and inner cell layers. (E) Pit field divided in two by an orthogonal cell wall. Scale bars=10 µm (A), 2 µm (B), 200 nm (C), 1 µm (D), 500 nm (E).