Morphology of the gynoecium in Labiatae

Two gynoecial primordia are initiated as discrete units but soon get interconnected by the occurrence of interprimordial growth between them. A rim of meristematic tissue thus produced gives rise to the ovary wall by zonal growth. The residual floral apex grows parallel to the gynoecial primordia in the form of a septum. The two placental ridges arise from the inner lateral walls of the ovary, grow into the ovarian cavity, and ultimately fuse with the axial septum. The anterio- posterior region of the ovary wall also grows into the ovarian cavity to form a false septum which divides each locule into two. The Labiatae show a placentation which is neither true axile nor true parietal but an intermediate condition between the two, as the septum grows like in a typical axile placentation and the placentae like in typical parietal placentation. The gynobase in Labiatae is considered to be carpellary in nature.