Earlier reports (Thompson 1968, 1970a, b), described experiments with seed of species of Caryophyllaceae obtained from the living plant collections at the Royal Botanic Gardens, Kew, or from wild populations growing in different parts of Europe. The results showed that certain parameters of the germination response-in particular the speed of germination at low temperatures, the maximum and minimum temperatures at which germination occurred, and the overall temperature span favouring germination-could be correlated with the geographical distribution of individual species. Thus, the temperature responses found for the germination of species distributed predominantly in deciduous woodland zones of Europe could be distinguished from those found for species growing around the Mediterranean, and, in turn, from those in steppeland areas of eastern and central Europe. However, species which have quite different overall geographical distributions may be found in any locality. Their occurrence in one area may result from natural overlapping of their ranges, from localized variations in edaphic conditions, or from the activities of man which may support aliens under conditions which are naturally unfavourable to the long term survival of the population. The observations reported here were made with a group of nine species all drawn from the sub-family Silenoideae of the Caryophyllaceae. The seed used had been collected during the summer and autumn of 1967 from wild populations growing around Halle in central Germany.