Genecologists have mainly concerned themselves with wild plant species occurring in natural floras, or in those disturbed by man. So far there has been little attempt to study the evolutionary ecology, in the broadest sense of the term, of cultivated plant species, more particularly of those varieties of fruits grown in orchards. In Britain new growers tend to confine their choice of fruit varieties to those already locally growing and cropping satisfactorily; they are also somewhat restricted to varieties suiting nearby markets. Yet these practices might themselves be influenced ultimately by the reactions of different varieties to local ecological conditions. Man, of necessity, grows only those plants which he wants, either because they are profitable or because he likes them. Just as there are differences in food preferences between peoples of different countries, so there may also be local differences in taste preferences between people in the north and in the south of the British Isles. Such a factor would influence, for example, whether sweet or sour cherries, or whether dessert or culinary apples are in local demand. There could also be geographical differences in the domestic uses of fruits, which would be reflected in the requirements of different markets. Thus probably more fruit-pies are eaten in mining and heavy industry areas (i.e. northern counties of England), whereas more dessert fresh fruit is eaten in areas of commerce and light industries (i.e., southern English counties). Furthermore, historical factors in horticultural practices of different regions will no doubt have played a role, so that orchards in the north and in the south of England may have evolved in different ways. In the hope of determining some of the basic factors inter alia which ultimately influence growers unconsciously in their preferences, it was decided to investigate the distribution of cultivated fruit-trees in Britain by using polyploidy as a biological yardstick, as previous investigations with polyploidy and wild species have proved profitable. The results besides having theoretical interest for evolutionists and geneticists might be of practical value to fruit growers. This paper, therefore, reports investigations on polyploidy in relation to the distribution of cultivated apples and cherries in Britain.