Conifers are wind pollinated with no reported restrictions on self pollination and self fertilization. Nevertheless, most species show large inbreeding depression in growth; and the frequency of self seedlings in wind-pollination progeny is generally low. In this paper the influence of embryo viability, polyembryony, and pregermination embryo selection on the relationship between natural self pollination and proportion of self seedlings is investigated. Species with low (coastal Douglas-fir) and high (noble fir) self-embryo viabilities are used as examples. In Douglas-fir, the main factor reducing the effects of self pollination is low viability of self embryos. Polyembryony and the potential for pregermination selection augment the effect of low self-embryo viability. Natural self pollination can reach 40-60% of total pollination without greatly increasing the proportion of self seedlings in the seedling population. In noble fir, polyembryony allows for embryo selection; but frequency of self seedlings increases nearly proportionately to any increase in natural self pollination. Other aspects of the mating system may limit natural self pollination or self fertilization in this species.
