Asplenium fontanum consists of two morphologically slightly different but geographically widely separated, diploid subspecies with homologous chromosomes (Reichstein & Schneller, [??citation]. 1982; Gibby, [??citation]. 1982). The typical subspecies, A. fontanum subsp. fontanum, only grows on limestone rocks in southern and central Europe. In Asia, it is replaced by this slightly different subspecies with somewhat wider fronds, deeply incised pinnae, and narrower segments. Its perispore is also slightly different with an outer perisporal layer with numerous small holes (fenestrate-reticulate).