Abstract Scleropogon brevifolius is a monotypic, disjunct, New World, colony‐forming, perennial grass. Its nomenclature is relatively uncluttered. Its floral biology has always been confusing in its detail. Dioecism in S. brevifolius is expressed in sexually dimorphic inflorescences, and in adjusted floral sex ratios between male and female plants. At Uspallata in Precordilleran Argentina the primary sex ratio is met for female plants in the population (F/n=0.5), but male plants at 0.149 depart from expectation. Analysis of the remainder shows it to consist of monoecious variants among which andromonoecism (0.186) is the most significant. The contribution of ovules and pollen to the next generation by females, andromonoecids, and males is ca 80%—the balance is from very low frequency trimonoecious, monoecious, and hermaphrodite elements. The projected pathway to dioecism is via monoecism, and the numerous intermediate sex forms in the population allow the identification of many positions o
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