Fleming T. H., Maurice S., Buchmann S. L., Tuttle M. D., Reproductive biology and relative male and female fitness in a trioecious cactus, Pachycereus pringlei (Cactaceae), American Journal of Botany, 1994, 81(7):858-867, doi: 10.2307/2445767
A study of two coastal Sonoran populations of Pachycereus pringlei documents male, female and hermaphroditic individuals. Pollination experiments and measurements of seasonal seed and pollen production describe functional differences between these forms. The paper also discusses limitations of models explaining the maintenance of trioecy.