Crocuspollen tubes following intra- and interspecific crosses, were removed from the ovary and examined by light and electron microscopy. Compatible pollen tubes (outcross) exhibit the typical organule distribution in the four major regions; in the apical region, globules are joined to plasma membrane and vesicles consisting of an electron translucent core and a homogeneously opaque halo are present. Intra- and interpecific rejections show identical ultrastructural pattern, indicative of a common incompatibility mechanism. The rejection pattern is comparable to that known for species with stylar rejection; some differences concerning wall changes are discussed in therms of a probable relationship between pistil structure and self-incompatibility (SI) mechanisms.