New observations on the fern genus Helminthostachys Kaulfuss (Ophioglossales) are presented. Tetrarchy of the stele in the root is confirmed. The stomata in Helminthostachys are similar to those in Ophioglossum palmatum. The unusual structure of the vegetative laciniae found at the distal end of each sporangiophore is again emphasized. In the rhizomes the presence of a periderm could be demonstrated.