CRETACEOUS AND TERTIARY PLANTS OF EUROPE The plant deposits of Europe, though numerous, are usually of limited extent and confined to small areas. When intercalated with marine beds the geological age may be clear ; but frequently this does not happen, and then the age is doubtful, unless the de posits contain the remains of land animals, which sometimes help in correlation.
By the Upper Cretaceous, flowering plants begin to dominate, and from various parts of central Europe a considerable number of species have been recorded. In Bohemia, besides conifers and ferns, there occur many dicotyledons. Credneria is a genus of unknown affinity, but other plants have been referred to living genera. Such are Myrica, Ficus, Quercus, Eucalyptus, Pisonia, Phillyrea, Rims, Prunus, Bignonia, Laurus, Salix, Benthamia. But without the evidence of fruits or flowers in support, it is difficult to believe that so many living genera existed.
After the Cretaceous there was an interval of unknown dura tion not represented by deposits in Europe. The Tertiary period which followed witnessed great changes in the physical geography of the continent. The great mountain-chains which span Eurasia were uplifted. As we shall see later this has had an enormous influence on the plant life of these regions ever since. In addition to mountain-building, there was also great volcanic activity in various parts. It is customary to divide the Tertiary into four periods : Eocene, Oligocene, Miocene, Pliocene.
Eocene.—The earliest Eocene, the Paleocene, is not repre sented in Britain, but is found on the Continent in the north-east of France, and in Belgium. The flora is still close to that of the Upper Cretaceous, and indicates similar warm-temperate or sub tropical conditions. Count G. de Saporta recorded from Gelinden, near Liege, species of oak, chestnut, laurel, cinnamon, camphor, Litsea and Persea; also members of the Araliaceae, Menisperma ceae, Celastraceae and Myrtaceae families. From tufa formed by an ancient waterfall at Sezanne he recorded, besides a profusion of ferns, genera of Lauraceae, Tiliaceae, Meliaceae, Sterculiaceae; also Symplocos, Artocarpus (the bread-fruit), Magnolia, hazel, alder, willow, viburnum, cornel, fig, ivy and vine ; but nearly all the European genera show an exotic character. From the Paleo
cene near Paris, Watelet recorded Araucaria, bamboo and palms. Later in age are the Woolwich and Reading series of England from which a small but interesting flora suggests a rather more temperate climate than that which preceded or followed it. Leaves of plane are abundant, and among the plants recorded are Robinia, a palm, two figs and a laurel. C. von Ettingshausen and J. Starkie Gardner who worked on the beds, recorded two ferns, Aneimia and Pteris ; and two gymnosperms, Libocedrus, related to the American L. decurrens, and a species of swamp cypress, Taxodium europaeum.
The Oldhaven beds which follow have yielded fig and cinnamon. None of these beds have as yet been fully investigated, and the evidence is too scanty for a correct inference as to climate.
The deposit next in age in England to which we must refer is the London Clay. It is the most important plant bed of Lower Eocene age in Europe. The fruits and seeds are very abundant and beautifully preserved. For more than two centuries they have attracted attention. In 1840 Dr. James Scott Bowerbank pub lished an admirable study of some of them, but the work was never finished. His botanical knowledge was inadequate to allow him to determine the species. In 1879 Ettingshausen made a very hurried study of Bowerbank's material, and published a list of plants, but without any evidence to support his determinations. Critical examination of the same material by the writers, who are now engaged upon its study, proves that his work was faulty in the extreme and valueless. The work of revision is not com pleted, but it may be stated that, with the exception of a few representatives of sub-tropical genera, the affinity of all is tropical. Scarcely any of the genera have living representatives in Europe. The Nipa palm was one of the commonest species. In the present era it abounds on the margins of estuaries and lagoons in the tropics of east Asia. Other palms are common, and families wholly tropical find representation. It can scarcely be doubted that the climate of Britain was tropical, or nearly so, when the London Clay was deposited.