Figure 1

PDMPO-labelled silica deposition in horsetail. a. Rhizome; b. Basal stem, arrows (main and insert) indicate punctate deposits of silica associated with cell walls; c. Basal stem, arrow (insert) indicates silica deposition at cell plate between dividing cells; d. Basal stem, arrow (insert) indicates punctate deposits of silica associated with highly invaginated cell walls; e. Distal stem, showing (main and insert) rosette-like silica structures and heavily silicified stomata; f. Node, showing high density of silicified structures including doughnut-like pore (insert); g. Node, showing jagged appearance of silica-rich cell walls; h. Leaf, showing high densities of rosette-like silica structures; i. Leaf, demonstrating the intimate association of silica with stomata (insert); j. Spores, showing heavily silicified spores including (insert) punctate deposits of silica on the spore surfaces. Scale bars; 100 μm - d,e,f,g,h,i; 200 μm - a,b,c,j.