胎盤形成; 胎座式
Placentation \Plac`en*ta"tion\, n. 1. (Anat.) The mode of formation of the placenta in different animals; as, the placentation of mammals. 2. (Bot.) The mode in which the placenta is arranged or composed; as, axile placentation; parietal placentation.
placentation n 1: the formation of the placenta in the uterus 2: arrangement of the ovules in the placenta and of the placentas in the ovary