Summary.Seeds niPolygonum lapathifoliumfrom several sources or after certain treatments were subjected to various periods of moist chilling and then incubated for 3 weeks, during which time the numbers that germinated were recorded.Populations from different localities differed in both seed weight and in the response of the seeds to chilling, but no relationships between the response and the environment of the locality of origin were found. Seeds from individual plants and from single inflorescences within populations also varied in both seed weight and germination with and without chilling. Application of dichlorprop to the parent plants was found to affect seed weight and % germination, the effect varying with both population and dose.Etudes sur des espèces de mauvaises herbes du genre Polygonum L.IV.Variations du poids et des modalités de germination des semences chezP. lapathifolium