Seeds of wild Digitalis purpurea from 150 different areas in 20 counties of Great Britain have been collected; weight of 100 seeds was 3.5–8.6–11.6 mg. Each batch of seed, regarded as a clone, was grown under uniform conditions and leaf collected from both first year and second year plants. Glycosidal content of each leaf sample, drawn from 8 plants within the clone, was estimated using 3,5‐dinitrobenzoic acid and results expressed as u./g. by comparison with the Standard Preparation of Prepared Digitalis. Values for clones were: first year 9.8–13.7–18.9 u./g.; second year 3.1–7.6–11.4 u./g. Clone values for dried leaf yielded per plant were: first year 38–79–137 g.; second year 12–23–47 g. The weight of parent seed does not affect the yield of leaf or its activity (first year); nor is leaf activity affected by leaf yield (first year). A positive relation existed for first and second year leaf activity values for each clone and suggested genetical control of activity.