Outcrossing rates in natural populations of Lupinus nanus Dougl. have been found to vary from nearly zero to nearly 100 percent (Harding and Horovitz, 1969; Harding, 1970). These studies were based primarily on a group of northern populations of subspecies apricus (Elliott, Harding, and Mankinen; paper VI). The purposes of this paper are (I) to report estimates of outcrossing for the other subspecies of L. nanus, (2) to report estimates of outcrossing for the closely related species, L. bicolor, L. affinis, L. polycarpus, and L. paehylobus, (3) to discuss the relationship between these estimates of outcrossing and autofertility, and (4) to discuss the relationship between outcrossing and phenotypic and genotypic variability maintained in populations. OUTCROSSINGRates of outcrossing have been estimated by progeny testing genetically recessive parents occurring in natural populations of Clarkia (Vasek, 1964(Vasek, , 1965(Vasek, , 1967, Avena (Jain and Marshall, 1967), and Lupinus (Harding and Horovitz, 1969; Harding, 1970). In Lupinus nanus rare flower color mutants (Harding and Mankinen, 1967) are convenient genetic recessives for the estimation of outcrossing. These recessives are also found in the other species of the Nanus Group.The expected frequency of genetically dominant outcrosses arising in progeny of recessives is a(l-q) where a is defined as the frequency of out-* Supported in part by NIH training grant GM 701. -The editor gratefully acknowledges partial financial support towards publication.

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