Species of Dryopteris dilatata complex in Perm region

Difficult-to-distinguish species of Dryopteris dilatata complex are analyzed from the perspective of Komarov's plants species theory. As a result, the frequent intersection of D. expansa (C. Presl) Fraser-Jenkins & Jermy and D. dilatata (Hoffm). A. Gray in the attribute space is noted. It allows to characterize them as extreme "forms" with a mass of transitional forms. In this case we can speak about indistinct morphological systems which however have a geographical certainty. D. dilatata is a typical "form" for western and central Europe, D. expansa for Eastern Europe, Urals, Siberia and North America. Thus the recognition of chromosome races referred to as D. dilatata and D. expansa as independent species is justified by their geographical certainty. Though, in the case of D. assimilis S. Walker such certainty isn't observed. The last binomial belongs to indistinct morphological system with the absence of geographical certainty.