The spores of the recent fern Pteridium aquilinum (L.) Kuhn are studied in comparative aspect with the morphologically similar spores from the Late Pleistocene (Valdaian) paleosoil (fossil soil, FPS-profile), which is outcropped in temporal sections in northern-eastern part of Ramenskoe (Moscow region). Adult well-developed spores of Pteridium aquilinum are of a larger size and bear thick sporoderm having fine granulate sculpture. Weakly developed young spores are of smaller size and bear thinner and smooth sporoderm. Young spores mostly are of subtrianular shape. Well-developed adult spores are more or less round. Most of the studied spores of Pteridium aquilinum are trilete, with the well-formed trilete mark (tetrad scar). Sometimes the trilete spores with one shortened ray occur. The third ray may be even completely reduced, and the spore becomes being monolete. The size of the sporangia of Pteridium aquilinum also widely vary even for one and the same fertile pinnule. The sporangia disposed on longer distance from the pinnule margin have shorter sporangiophores and smaller size. The diameter of such sporangia is smaller than the diameter of the well-developed sporangia almost in three times. The high variability of the in situspores and the size of the sporangia is recorded on the basis of the present study. This observation should be taken in account during any research concerning reconstruction of taxonomical diversity of fossil palynofloras.