A simple method for fixing and embedding plant tissue for hybridization histochemistry has been developed. Material is fixed with paraformaldehyde-glutaraldehyde by the phase-partition technique and embedded in LR Gold. The method preserves nucleic acids in situ. Double-stranded 32P-labelled DNA probes hybridized to complementary RNAs in thin and semithin sections. Biotinylated probes detected with immunogold markers have been used to localize transcripts at the electron microscopic level.