AbstractProgenies of seed of raspberry (Rubus idaeus L.) harvested wild from 15 English, 7 Scottish, 4 Welsh, 2 German and 2 Swiss sources were studied in the field. No new genes were found. All seedlings examined were diploid (2n = 14), but one rosette plant failing to flower had diploid and tetraploid shoots. The frequencies of spine colour, habit, leaf colour and leaflet number varied; one family segregated spineless plants. Most plants were hairy, in contrast to earlier reports. Investigations were made on flower bud development and flowering times; five families segregated for autumn flowering. Analyses were also made on dieback, vegetative bud-break, flower bud development, annual variation in flowering-time and fruit ripening. These biometrical characters are not essentially related to geographical origin. Male plants with healthy pollen occurred in 3 families. Males are possibly more sensitive to environment than hermaphrodites; a cycle-is given to illustrate how male plants are maintained in natural populations. Six families segregated non-red fruits. Ripe fruits are mostly deep purplish-red, and markedly smaller than those of cultivated varieties. Some families had large, good flavoured fruits, suggesting derivation or introgression from cultivated varieties. The frequencies with which 7 genes were segregating in the families show a Poisson distribution. Wild raspberries are remarkably homozygous, the maximum number of heterozygous genes found in a family being four. The differences between wild and cultivated raspberries are considered in relation to the origin of 'Lloyd George': wild plants usually produce many short, hairy canes, whereas cultivated varieties mostly have tall, few, subglabrous canes. The spineless character should be of use in raspberry breeding. The absence of a recognisable cline in wild British R. idaeus may be attributable to Great Britain representing only a relatively small area of the natural distribution.