Darwin (1877) suggested that the resources allocated to reproduction differ between the sexes in certain species of dioecious flowering plants. Recent workers have postulated that differential expenditure on reproduction between sexes may account for the unequal sex ratios found in many dioecious species (Harris, 1958; Putwain and Harper, 1972; Lloyd, 1973; Lloyd and Webb, 1977; Melampy and Howe, 1977; Grant and Mitton, 1979; Hancock and Bringhurst, 1980). However, there is a lack of quantitative data concerning differences in reproductive effort of males and females under field conditions. It may seem intuitively obvious that females allocate greater amounts of resources to reproduction due to the requirements of fruit and seed development, but the extent and pattern of differences throughout the reproductive period have not been documented in natural populations. Although sex ratios of unity have been reported, deviations from this are frequently observed (Lloyd, 1973, 1974; Opler and Bawa, 1978; Hancock and Bringhurst, 1980; Webb and Lloyd, 1980). Lloyd (1973) has related biased sex ratios to life history, arguing that male-biased ratios tend to occur in iteroparous perennials of great longevity. Under the assumption that reproductive effort is greater in females, and that some limitation to energy expenditure exists, repeated flowering would restrict clonal propagation in females compared with males. This would result in an increase in the number of male relative to female inflorescences. Malebiased ratios, then, are explained as a consequence of repeated reproduction rather than as a result of direct selection. Aralia nudicaulis (wild sarsaparilla) is a rhizomatous perennial that occurs throughout the boreal forest zone of North America with extensions south into shaded woodlands of the U.S.A. Aralia nudicaulis is dioecious, possessing flowers of one sex only on a given individual. Rare flowering shoots contain perfect flowers (Scoggan, 1979) or separate male and female flowers. These floral types were found in less than 1% of the flowering shoots sampled for this study and are not considered further. In common with many of the herbaceous understory species of the boreal forest (e.g., Pteridium aquilinum, Clintonia borealis, Cornus canadensis), A. nudicaulis forms extensive clones which are probably of considerable age. Clonal growth in A. nudicaulis results from an extensive, subterranean rhizome system. Typically, clones (genets) are composed of scattered aerial shoots (ramets) which are either vegetative or reproductive. All ramets have a single, ternately compound leaf borne on a long petiole. In flowering ramets, this is subtended by a short naked scape terminated by a single umbellate inflorescence. The leaf and inflorescence are born on a short vertical shoot which arises from the underground rhizome. Fragmentation of underground parts as well as the complexity and extent of the rhizome system make identification of individual genets virtually impossible. Hence, in this study, all references to sex ratio refer to the sex ratio of flowering ramets. Field observation during 1978 indicated that a greater number of male than female flowering ramets occurred in forest sites of central New Brunswick, Canada. To extend these observations, surveys of ramet sex ratio in different habitats were made during 1979 and 1980. In order to compare