Fig. 148.—Trigonia margaritacea. (Living form.)
THE EOCENE PERIOD.
During this period terra firma has vastly gained upon the domain of the sea; furrowed with streams and rivers, and here and there with great lakes and ponds, the landscape of this period presented the same curious mixture which we have noted in the preceding age, that is to say, a combination of the vegetation of the primitive ages with one analogous to that of our own times. Alongside the birch, the walnut, the oak, the elm, and the alder, rise lofty palm-trees, of species now extinct, such as Flabellaria and Palmacites; with many evergreen trees (Conifers), for the most part belonging to genera still existing, as the firs, the pines, the yews, the cypresses, the junipers, and the thuyas or tree of life.
The Cupanioides, among the Sapindaceæ; the Cucumites, among the Cucurbitaceæ (species analogous to our bryony), climb the trunks of great trees, and hang in festoons of aerial garlands from their branches.
The Ferns were still represented by the genera Pecopteris, by the Tæniopteris, Asplenium, Polypodium. Of the mosses, some Hepaticas formed a humble but elegant and lively vegetation alongside the terrestrial and frequently ligneous plants which we have noted. Equiseta and Charæ would still grow in marshy places and on the borders of rivers and ponds.
It is not without some surprise that we observe here certain plants of our own epoch, which seem to have had the privilege of ornamenting the greater watercourses. Among these we may mention the Water Caltrop, Trapa natans, whose fine rosettes of green and dentated leaves float so gracefully in ornamental ponds, supported by their spindle-shaped petioles, its fruit a hard coriaceous nut, with four horny spines, known in France as water-chestnuts, which enclose a farinaceous grain not unpleasant to the taste; the pond-weed, Potamogeton, whose leaves form thick tufts of green, affording food and shelter to the fishes; Nympheaceæ, which spread beside their large round and hollow leaves, so admirably adapted for floating on the water, now the deep-yellow flowers of the Nenuphar now the pure white flowers of the Nymphæa. Listen to Lecoq, as he describes the vegetation of the period:—“The Lower Tertiary period,” he says, “constantly reminds us of the tropical landscapes of the present epoch, in localities where water and heat together impress on vegetation a power and majesty unknown in our climates. The Algæ, which have already been observed in the marine waters at the close of the Cretaceous period, represented themselves under still more varied forms, in the earlier Tertiary deposits, when they have been formed in the sea. Hepaticas and Mosses grew in the more humid places; many pretty Ferns, as Pecopteris, Tæniopteris, and the Equisetum stellare (Pomel) vegetated in cool and humid places. The fresh waters are crowded with Naiades, Chara, Potamogeton, Caulinites, with Zosterites, and with Halochloris. Their leaves, floating or submerged, like those of our aquatic plants, concealed legions of Molluscs whose remains have also reached us.
“Great numbers of Conifers lived during this period. M. Brongniart enumerates forty-one different species, which, for the most part, remind us of living forms with which we are familiar—of Pines, Cypresses, Thuyas, Junipers, Firs, Yews, and Ephedra. Palms mingled with these groups of evergreen trees; the Flabellaria Parisiensis of Brongniart, F. raphifolia of Sternberg, F. maxima of Unger; and some Palmacites, raised their widely-spreading crowns near the magnificent Hightea; Malvaceæ, or Mallows, doubtless arborescent, as many among them, natives of very hot climates, are in our days.
“Creeping plants, such as the Cucumites variabilis (Brongn.), and the numerous species of Cupanioïdes—the one belonging to the Cucurbitaceæ, and the other to the Sapindaceæ—twined their slender stems round the trunks, doubtless ligneous, of various Leguminaceæ.