Self-fertilization requires less energetic expenditures than cross-fertilization and benefits from a 50% advantage in its rate of gene transmission. Yet, no plant species is known that reproduces exclusively via self-fertilization, as all appear to maintain a certain outcrossing rate. I test the hypothesis that, under specific circumstances, cross-fertilization provides short-term advantages over self-fertilization in Corydalis sempervirens, a self-compatible winter annual. / Some fitness components of selfed and crossed progeny were compared under different experimental conditions. Crossed progeny derived short-term advantages from both their higher mean individual heterozygosity and their greater genotypic diversity. Overall, they had higher mean fitnesses than selfed individuals (heterosis), especially in favorable environments. Crossed progeny also displayed greater constancy of yield under increasing densities. In all test-environments, the few individuals with highest fitness resulted from outcrossing. However, as a group, crossed offspring did not have higher fitness values than selfed offspring and not all crosses generated progeny with equally high fitness. The fittest individuals were produced in crosses between parents which shared an intermediate number of common ancestors.

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