On the interrelationships of certain species of Petunia IV. Hybridization between P. linearis and P. calycina and nomenclatorial consequences in the Petunia group

Interspecific hybridization between the 18-chromosomes species Petunia linearis and P. calycina yields fertile and vigorous progeny. Analysis of meiotic prophase microsporocytes of the hybrids reveals bivalents with almost complete pairing, indicating large scale homology between both genomes. Moreover, they have a specific arrangement of petals in the flower bud. For these reasons, generic separation is proposed of the 2n = 18 species and the 2n = 14 species formerly referred to Petunia, the latter to be transferred to the genus Stimoryne, as S. axillaris (Lam.) Wijsman comb, not., S. integrifolia (Hook.) Wijsman comb, nov., and S. hybrida (Hook.) Wijsman comb. nov. From analogy, all described species of Petunia remain in Petunia except four additional very rare species for which new combinations are proposed.