Behaviour of elongating pollen tubes in the upper style ofGrevillea banksiiis described. Two populations of cytoplasmic vesicles (large and small) and early stages of callose plug formation were observed. No disfunction of self-tubes was noted that suggested incompatibility rejection. Burst tubes on stigmatic surfaces appear unrelated to incompatibility. Stigmatic and transmitting tissues are unaffected by passage of pollen tubes except for cells in direct contact which may appear crushed. Selfed flowers set seed in a field trial; emasculated ones, despite early swelling of the ovary in some, aborted within 8 wk. Reduction of tube number to two, equal to the number of ovules in the ovary, is attributed to heavier competition as the transmitting tissue narrows basally. In late stages of pollen tube interaction with the ovary, haustorial connections with ovary wall tissues occur, probably of post-fertilisation origin. Such distinct features of growth and ultrastructure as were seen are likely to be of adaptive rather than phylogenetic origin.