In the fern Polypodium vulgare L. increasing spore age leads to a decline in spore viability. It is suggested that the sigmoidal form of the survival curve is related to the fact that the spores of the cytotype used in the investigation are probably triploid. The other effects of increasing age include an increasing delay in germination, a decrease in the rate of germination, and an increase in the proportion of abnormal gametophytes. To some extent these effects are alleviated by high population density and low light intensity. Evidence is presented that the effects of age may be partly attributable to the declining ability of the spores to synthesize metabolites essential for germination and gametophyte development.