“…In Drenthe, according to Van Zeist (1955) (Firbas, 1949 (Eshuis, 1946;Schubert, 1933 (Pohl, 1937;Hyde and Williams, 1945), the distance over which the pollen grains of this entomophilous tree are transported, is but small (Rempe, 1937 According to Barkman (1948) Thelypterideto-Alnetum (Westhoff, 1956: Beekbergerwoud; Van Dijk and Westhoff, 1955 Firbas (1928), Zeidler (1953), and Koch (1944), Tilia (especially Tilia platyphyllos) requires a very humid climate. In the Hautes-Fagnes (Persch, 1950), on account of the large extent of the bog and perhaps also on account of the poor character of the soil, neither Tilia nor Ulmus exceeds Quercus, though the percentage of Alnus is low.…”