The placentas often occur in distinct lines called lines of placentation. The number of ovules is arranged on a central axis in a multilocular ovary. Within the ovary, each ovule is borne by a placenta or arises as a continuation of the floral apex. If the ovary is divided, with the ovules born on a line of placentation at the inner angle of each locule, this is axile placentation.
Free-central placentation occurs in bi or multicarpellary but unilocular ovary. Placentae develop along the fused margins of the adjacent carpels. Number of placentae corresponds to the number of carpels, e.g. Cucurbita, Dianthus, primrose etc.