AbstractIn a recent publication HORN (1997: 9) enthusiastically states that with the study by STOOR et al. (1996), which he co‐authored, “the biosystematics of Diphasiastrum in Europe has finally been resolved”. These authors present a scheme showing six taxa, three basal taxa (Ausgangsarten) and three taxa of hybrid origin in a triangular form to illustrate the relationships of European Diphasiastrum and they include a new taxon of hybrid origin, D. oellgaardii. The evidence for the origin and identity of D. oellgaardii is based solely on molecular data derived from allozyme electrophoresis. The interpretation of the allozyme data presented by the authors is open to dispute. The analysis of their data appears to be incorrect as STOOR et al. (1996) misapply the concept of additive banding patterns and fixed heterozygosity to homoploid hybrid taxa. Furthermore, the photograph in STOOR et al. (1996) of D. oellgaardii at its type locality resembles a growth form of D. alpinum frequent in the British Isles. In the light of these concerns we recommend caution and suggest that this name should not be adopted for individuals apparently intermediate between D. alpinum and D. tristachyum until further research is presented.