Nanoscale Similarities in the Substructure of the Exines ofFagusPollen Grains andLycopodiumSpores

The exine substructure of an angiosperm, Fagus sylvatica (beech) pollen and a pteridophyte, Lycopodium clavatum (a club moss) spore was investigated by scanning tunnelling microscopy. These pollen and spores, despite their distinct differences in structure and morphology on a micrometre scale, have very similar substructure on a nanometre scale. The substructure appears to consist of a multi-helix, i.e. a helical chain in turn wound into a helix with a self-similarity at smaller and smaller length scales. A simple vectorial form is proposed to describe quantitatively the multi-helical substructure.