Characteristics of indusia and sori in the two subspecies of Pteridium aquilinum (L.) Kuhn. occurring in Poland

Two subspecies of Pteridium aquilinum (L.) Kuhn: subsp. aquilinum and subsp. pinetorum occurring in Poland have been studied with respect to their micromorphological traits, in order to facilitate their differentiation. The micromorphology of marginal sori typical to Pteridium are described. Differences were found in the width of the outer membrane of indusium, the features of its edge (straight/notched) and the size and shape of the indusium cells. Moreover, the differentiating features turned out to be the frequency and length of the cillia on the edge of the indusium.