In situ hybridisation applied to chromosomes of orchid species. Blue DAPI staining shows chromosomal DNA (A, D, G, respectively Ophrys tenthredinifera, Serapias vomeracea and Himantoglossum hircinum); red and green signals show sites of hybridisation of 18S-25S rDNA and 5S rDNA respectively (B, E, H, C, F, I). Arrows indicate sites. Ophrys tenthredinifera ( B) three 18S-25S rDNA sites and (C) four 5S rDNA sites. Serapias vomeracea (E) six 18S-25S rDNA sites and (F) four 5S rDNA sites. Himantoglossum hircinum (H) four 18S-25S rDNA sites and (I) four 5S rDNA sites.