An attempt was made to map the distributions of some of the individual clones of Trifolium repens in an area of about 600 sq. yd of fixed dune vegetation. The field observations were checked in culture by morphological examination and by cross-pollination. Most of the clones were limited to small patches of land (up to 6 yd across) and in relation to the vigorous vegetative spread of the species this might indicate a maximum age of genotype of about 20 years. However, one clone was found to be distributed in five discrete patches, each of small size but collectively giving a discontinuous spread of more than 20 yd. The five patches were limited to a narrow ecological zone suggesting specialization in ecological tolerance. The presence of a second genotype which occurred in two patches ecologically similar to one another but contrasting strongly with those of the first genotype indicated differentiation of ecological tolerance between genotypes within the population. These results are contrasted with those published earlier for Festuca. It is pointed out that if vegetative spread is limited by ecological factors the size of the area occupied by a clone cannot be regarded as a function of age, and that consequently the Trifolium genotypes observed might be just as ancient as those of Festuca.