Résumé
This paper discusses the main steps leading to the acquisition, during the Palaeozoic, of the seed habit. The earliest spermatophytes originated in the Late Devonian and produced small cupulate ovules characterized by an elaborated sporangial apex involved in pollination. The diversification of ovules during the Carboniferous led to a wider range of sizes and shapes, and an increasing importance of the integument. The earliest seeds containing embryos are reported in Carboniferous coniferophytes.