 He also wrote extensively on the mistletoe family of Loranthaceae, with much of his taxonomic work surviving to the present day.Van Tieghem's primary grouping was into "embranchements" (branches), followed by "sous-embranchement" (sub-branches), classes, orders, families, genera, species and varieties.His four branches (1st edition) were, as follows, with the Phanerogames divided into two sub-branches.