Twenty-two species of Sinningia were crossed together in 433 (94%) of the 462 combinations possible, and in all possible combinations excluding reciprocals. One hundred and two hybrid combinations were obtained, and their fertility was studied, as was the inheritance of interspecific differences. Sinningia was shown to consist of two types of species: bee-pollinated species, belonging to a number of small cenospecies, each containing one to a few species; and bird-pollinated species, mostly belonging to one of two larger cenospecies, each containing a diversity of species. Based on the relatively small numbers of genes demonstrated to control pollinator-specific floral differences between species within cenospecies, cenospecific limits are recommended as a good guide to sectional limits in future revision of this genus.
Interspecific Hybridization in Sinningia (Gesneriaceae