Flora van Nederland Haeckel (1866) - plants
   Division Spermatophyta Goebel (1882) see Phylum Spermatophyta Goebel (1882)
     Subdivision Angiospermae J. Lindley (1830) see Infraphylum Angiospermae auct.
       Class Dicotyledones see Class Magnoliopsida Brongn. (1843)
         Order Fagales Engl. (1892)
           Family Betulaceae Gray (1822), nom. cons. - birch family
             Genus Alnus Mill. (1754)
               1 Alnus cordata (Loisel.) Duby (1828)
               2 Alnus glutinosa (L.) Gaertner - black alder
               3 Alnus incana (L.) Moench - gray alder
               4 Alnus glutinosa × incana