Germination tests were done on thermo-gradient bars with diaspores of different types and cultivars of small-seeded vegetables commonly grown in the UK. Considerable differences were found between the responses of different types of vegetable expressed as variations in the time course of germination at different temperatures, and the upper and lower temperature limits at which germination occurred. Variations in the responses of different cultivars of particular vegetables were relatively small, especially at low temperatures, except in the case of onions for which quite considerable variations in temperature minima were identified. Methods of expressing the interaction of time and temperature on the course of germination were compared and it was concluded, in each case, that although an approximate, and sometimes adequate fit could be obtained by using a linear regression to plot temperature against the reciprocal of time, a much better representation was obtained by the use of a polynomial equation. In the discussion it is suggested that the temperature responses of vegetables have changed little, if at all, during their period of cultivation by man, and that the possession by a species in the wild state of a germination response incidentally pre-adapted to the requirements of cultivation, might have been a major factor influencing the probability of its adoption as a cultivated plant by mankind.