Whole-cell labelling of Zygnema S. Young (A,C,E,F,H) and old (B,D,G,I) filaments labelled with the monoclonal antibodies LM15, 400-4, 400-3 or LM10 (green). In the confocal micrographs in A and E, one optical section is shown, confocal micrographs in B–D and F–I show z-projections of ∼50 optical sections. The corresponding bright-field images include red chloroplast autofluorescence. (A) Detaching cells with staining in exposed cell walls. (B) Staining in outer and cross cell walls but not in ribbon-like zones close to cross cell walls. (C) Similar pattern to that shown in B. (D) Staining in outer cell walls. (E) Filament with patchy labelling in outer cell walls. (F) Circular staining underneath expanded terminal cross wall. (G) Central cell showing patchy straining, which is weak in adjacent cells. (H) H-shaped cell wall structure with staining in three distinct rings. (I) Prominent H-shaped cell wall structure with strong staining. Young filaments are 1 month old; old filaments are 12 months old. Scale bars: 10 µm.