Gradients in ovule development on multiovulate placentae. (A–C) Acropetal and basipetal development of ovules on the placenta (and reduction of last formed ovules in some cases). (A) Basipetal. Solanum sisymbrifolium. (B) Acropetal, upper ovules reduced. Liquidambar orientalis. (C) Acropetal, upper ovules greatly reduced. Corylopsis willmottiae. (D–F) Peripheral delay in development. (D) Passiflora holosericea. After ovule initiation. (E) Passiflora holosericea. After integument initiation. (F) Nymphaea tetragona. Scale bars: (A, D, E) = 0·05 mm; (B, F) = 0·2 mm; (C) = 0·1 mm.