Actavia 0 Gudin, S. Arene, Laurence Chavagnat, A. Bullard, Camille 1991 1991-7-1 262-267 Rose achene imbibition is difficult. Comparison of sulphuric acid treated, Cross and Beavanś reagent (C. B. reagent) treated seeds with untreated seeds showed that, during imbibition, water is essentially found in the most external pericarp layer. Inner layers appear less permeable. It is possible to distinguish three layers in the pericarp by taking into account results from imbibition assays, X-ray radiographies and scanning electron microscopic observations. They can be interpreted as representing the epi-, meso- and endocarp. 4 33