Fern spores

 Occasionally fern spores can be found in dust samples. These spores often show a complex surface structure with ridges, papillae, granulations and pores in species-specific patterns. The ferns constitute a class within the phylum Pteridophyta, which are vascular plants that neither flower nor produce seeds. They replicate by spores that are produced within sporangia assembled in clusters (sori) typically on one side of the frond. Once mature, the spores are flicked out of its sporangium and dispersed into the air. Although of rather large size the spores are easily carried away by wind movements and may be carried long distances. Due to the sporopollenin content in the outer (exine) cell wall, the spores are very resistant to degradation.