Extrafloral Nectaries in Solanum

Extrafloral nectaries (EFNs) occur on the corollas of 3 dioecious species of Solanum (S. cunninghamii Benth., S. dioicum W.V. Fitzg., and S. tudununggae Symon) from Australia. Solanum dioicum also bears EFNs on the leaves. This is the first report of nectaries of any kind for the genus Solanum, the first report of EFNs for the family Solanaceae, and only the third genus from the 8 families in the order Solanales to be shown to possess EFNs. The EFNs are structurally complex and seem to function during the bud stage during which time they are actively visited by ants. SOME SORT OF NECTAR REWARD iS found in many, perhaps most, species of angiosperm flowers. Genera without floral nectar that offer other rewards (such as pollen or oil) are the exceptions. The large genus (ca. 2000 spp.) Solanum L. (Solanaceae) is one of these exceptions in that it offers only pollen as a reward (Symon 1979, Bancher and Holzl 1959); no species are known to bear floral nectar (Symon 1979). Thus, it is not surprising that there are also no reports of extrafloral nectaries for the genus (T. Elias 1983, and pers. commun.; Fahn 1979).2 In this paper we give the first detailed report of extrafloral nectaries (EFNs) for the genus and for the family. Herein we follow the current and reasonable practice in utilizing Delpino's (1874) functional definition of EFNs as nectaries on any plant organ, including parts of the flower, which do not function as sources of nectar rewards for