The effects of peeling and wounding on the IAA and fusicoccin (FC) growth response of etiolated pea cv. Alaska stem tissue were examined. Over a 5-h growth period, peeling virtually eliminated the IAA response, but c. 30% of the FC response remained. Unpeeled segments wounded with 6 vertical slits exhibited significant responses to both IAA and FC, indicating that peeling did not act by damaging the tissue. Microscopy showed that the epidermis was removed intact and that the underlying tissue was essentially undamaged. Neither the addition of 2% sucrose to the incubation medium nor the use of a range of IAA conc. down to 10-8M restored IAA-induced growth in peeled segments, suggesting that lack of osmotic solutes and supra-opt. uptake of IAA were not important factors over this time period. It is concluded that, although the possibility remains that peeling merely allows leakage of H ions into the medium, it seems more likely that peeling off the epidermis removes the auxin responsive tissue.