Based on cell wall texture of root hairs, two groups can be distinguished within the 10 species of Equisetum listed in Flora Europaea. This distinction coincides with the division of the genus Equisetum into two subgenera: Equisetum (horsetails) and Hippochaete (scouring rushes). All species of the subgenus Equisetum have a helicoidal cell wall texture in young growing root hairs as well as in full-grown hairs. All species of the subgenus Hippochaete deposit an additional inner cell wall layer against this helicoidal layer when elongation has stopped. The microfibrils in this additional layer do not form a helicoidal texture, but are helically arranged, forming a Z-helix. The presence of a helical layer in full-grown hairs is not a prerequisite for growth in soil, but an exclusively helicoidal root hair wall texture might be favourable for life in water. The wall texture is not influenced by the consistency of the substratum.