Callose plugs continue to elongate in most ecotypes. Ws pollen tubes after 6 h (A) or 30 h (B) germination. Callose plugs of Wa pollen tubes after 6 h (C) or 30 h (D) germination. (E) and (F) Callose plugs of pollen tubes of the F1s from reciprocal crosses between An and C24. Arrows indicate callose plugs. Bars = 50μm.