The effect of storage at low temp. (4°C) on the germination and viability of Trapa natans seeds was investigated. Seeds were collected from Lake Candia, Italy, and separated into 2 groups. The first group was placed in nets, which were then suspended in the lake. The second group of seeds was immersed in tap water in plastic containers and stored in an environment-controlled chamber in complete darkness at 4°C. Germination tests were carried out from Oct. 1989 to Mar. 1990 at monthly intervals. The greatest germination was found to occur at a temp. range of 15-25°C. An enhancement of germination was obtained by the cold treatment during the dormancy period, whereas during the spring period, when the germination capability begins, no effect was detected. Long-lasting germination behaviour was identified in all the seeds analysed and it is suggested that this information may be of ecological significance.