Obdiplostemony in the genus Allium L.

Early floral organogenesis has been investigated in a number of Allium species from various subgenera and sections (A. I ramosum, A. angulosum, A. galanthum, A. sphaerocephalon, A. oreophilum, A. cernuum, A. moly). Comparative studies and earlier results show a considerable uniform pattern of the sequence of floral organ inception in the genus as a whole. Fusion of extended filament bases and shifting outwards of the originally inner stamina has been observed in Allium oreophilum after stamina differentiation only. A disturbance of alternation in the androeceum has been detected in Allium kujukense, A. umbilicatum, and A. ferganicum as well. Those configurations and that of Trillium apetalon can be described by the term "obdiplostemony", applied in a broad sense also to flowers with a perianth, not differentiated into calyx and corolla. According to this definition, mature flowers with two stamen whorls are obdiplostemoneous in the case of an interrupted alternation between androeceum and perianth, with stamina of the outer stamen whorl opposite the parts of the inner whorl of the floral envelope and/or stamina of the inner stamen whorl opposite the parts of the outer whorl of the floral envelope. In the genus Allium obdiplostemony occurs in several subgenera and sections of different flower traits. In the case of Allium oreophilum and A. kujukense however, a special type of obdiplostemony suggests a close relationship.