[Illustration: FIG. 163.—Flower and Leaf of _Bombax sepultiflorum_. Eocene of Aix.—After Saporta. A European representative of the Silk-cotton-tree of the East Indies and Tropical America.] Gradual elevation of the land favoured for a time the extension of these plants, and the warmth of the climate allowed them to extend even into Arctic latitudes. But in the middle of the Eocene another subsidence occurred, which exterminated much of the Eocene flora, and was perhaps accompanied with a reduction of temperature, in which the more northern lands became covered with great forests of trees allied to the Pines. In England a remarkable deposit of this age is that of Bovey Tracey, in Devonshire, where beds of clay and brown coal have afforded a rich flora of American and southern types. The _Sequoia_ shown in Fig. 164 abounds at this place, and is a near relation to the celebrated “big trees” of California; the _Cinnamomum_ in Fig. 165 is a type equally foreign from modern England. It is a curious feature of the Bovey deposit that immediately above these Eocene beds, holding a rich flora of warm temperate character, are glacial clays with leaves of Arctic willows and of the dwarf birch, indicating a climate much more severe than that of the British Islands at present.[75] [Illustration: FIG. 164.—Branch and Fruit of _Sequoia Couttsiæ_ (Heer). Eocene. England.] In the Miocene period the land again rose, and the northern flora spread itself southward equally over Europe, Asia, and America, so that the Miocene flora of all these regions is very similar; and this Miocene flora continues substantially to this day in Eastern America and Eastern Asia, except that it has been greatly reduced in number of species by the intervention of the cold glacial period; but in Europe and Western America it has been largely replaced by other apparently more modern species. [Illustration: FIG. 165.—_Cinnamomum Scheuchzeri_ (Heer). Eocene. England.] A striking result of recent discoveries is the fact that in Cretaceous and Eocene times a very warm climate prevailed in the extreme Arctic regions, and trees of temperate latitudes grew there freely. In the recent Arctic expedition, Captain Fielden found in latitude 81° 40’, within 600 miles of the Pole, a bed of lignite, from twenty-five to thirty feet in thickness, associated with remains of plants such as now grow only in temperate latitudes. “From the character of the plant-remains, Dr. Heer infers that the lignite of this locality represents an ancient peat-moss, which must have been of wide extent, with reeds, sedges, birches, poplar, and certain conifers growing on its banks; while the higher and drier ground in the neighbourhood probably supported a growth of pines and firs, with elms and hazel-bushes. The remains of water-lilies suggest the existence of a fresh-water lake in the old peat-moss, which must have remained unfrozen during a great part of the year.”