Calycanthaceae, sister to all other Laurales, are the most distinct family of the order in their gynoecium structure (lateral placentation, presence of two ovules). Gynoecium structure was studied in a representative of each genus of Calycanthaceae and gynoecium development in a representative of each of the two subfamilies (Calycanthoideae and Idiospermoideae). Newly found shared features are postgenital coherence between the free carpels (extragynoecial compitum), abortion of the upper of the two ovules, and lobation of the outer integument. Differences in reproductive structures between the two subfamilies are reviewed. Newly found differences include carpel primordium shape, contribution of the outer integument to micropyle formation, epidermis differentiation of the rim of the integuments, and mode of formation of the compitum. Unexpectedly, at anthesis, ovary and ovules of Idiospermum are not larger than those of Calycanthoideae, despite the conspicuous difference in fruit. The identity of “staminod...