Stamen development in Salvia L.:: Homology reinvestigated

The genus Salvia is characterized by lever-like modified stamens. The hypothesis of homology is reinvestigated by referring to three different levels of positional homology: ( 1) the position of the stamen within the flower, ( 2) the position of the lever within the stamen, and ( 3) the position of the reduced theca within the lower lever arm. Stamen development in twenty-one Salvia species from different sections and with highly diverse staminal structures is studied. Starting with an asymmetric anther, the thecae of which are separated by the widening connective, the general development is the same in all species. With few exceptions, all species develop only one fertile theca, while the second theca remains inhibited to a certain degree. The filaments in each species elongate in a later developmental step and form the joint that facilitates the lever-like movement of the connectives. Specific differences among the species refer to the time and degree of inhibition of the sterile theca, to the forming of secondary joint structures, and to the size, shape, and relative proportions of all staminal parts. The hypothesis of homology is confirmed in the first two levels of positional homology and rejected in the third. We always found the sterile theca at the end of the lower connective arm, but because of secondary growth processes, its relative position is different in the adult stage.