The biomass allocated to component organs of I. capensis varies between 2 populations living under extremely wet and dry conditions for the species. Seed output per gram and the percent of total biomass in component organs showed no appreciable differences. Under uniform greenhouse conditions there were no significant differences between the 2 Impatiens populations. Although growth of I. capensis is environmentally controlled, resource allocation is not. The same conclusions are obtained if reproductive effort is estimated by the number of viable seeds/gram of plant biomass.