100 COXIFElLi: OF THE TERTIARY PERIOD. 



been found in the Thames Valley, and of a true Cypress, ('iijn'cxxnx 

 ta-j'ifonnix, at Bournemouth. Two forms of a Taxodium also occur in 

 the Bournemouth beds, and also others that have been referred to 

 Sequoia ; in the London Clay have been preserved fruits of a Taxsid 

 closely resembling those of the Gingko ; and at Alum I Jay in the 

 Isle of Wight as well as in the London Clay have been detected 

 remains of the sub-tropical genus Podocarpus. Remains of the 

 foliage of an Araucaria occur in the Freshwater beds of the Isle of 

 Wight, and in the marine beds at Bournemouth ; pine cones in the 

 Thanet beds of Kent, at Bagshot, in the Isle of Wight and County 

 Antrim ; and from the basaltic formation in the same county and in 

 the Isle of Mull have been discovered cones of a Tsuga and branchlets 

 of a Cryptomeria.* 



In the Oligocene and Miocene systems of the Middle Tertiary period 

 are found large masses of carbon deposited in the earth in the form 

 of beds of "brown coal" or lignite, which are chiefly composed of 

 coniferous remains mixed with those of ancestral forms of ( v )uercus, 

 Magnolia, etc. The coniferous forests of that period did not, therefore, 

 exhibit a dull uniformity as is the case with those of the present 

 time ; there was, on the contrary, an abundant and cheerful variety of 

 forms as is seen even now in the forests of Canada and in parts of the 

 southern United States, though not to so great a degree. There must 

 have been enormous quantities of resin exuded by some of these trees, 

 which belonged to genera resembling Thuia, Cupressus, Sequoia and 

 Taxodium; this resin hardened by external conditions is now known as 

 amber. 



Towards the close of the Tertiary period, the gradual refrigeration of 

 climate already mentioned, reached its maximum. Under its influence 

 the coniferous trees that had flourished over the north Temperate zone 

 and far beyond the Arctic Circle in the earlier ages, disappeared, " the 

 Alps and Pyrenees were loaded with vast snow-fields from which enormous 

 glaciers descended into the plain, overriding ranges of minor hills on 

 their way. The greater portion of Britain was similarly ice-covered ; in 

 Xorth America also, Canada and the eastern States of the Union down 

 to about the 39th parallel of north latitude lay under the northern ice- 

 sheet."! As a natural consequence of this climatic change, the former 

 sub-tropical vegetation of central and northern Europe and of North 

 America was replaced as the ice-sheet receded northwards by an arctic 

 and sub-arctic flora which included but few coniferous species, but they 

 were spread over large areas. As we enter upon the recent and 

 pre-historic formations, the types of vegetation become essentially the 

 same as those now existing, and were spread over the same regions. 

 The paucity of species of coniferous trees in the regions affected by the 

 ice and snow of the Glacial period has remained unchanged except by 

 the agency of Man. The British flora includes only three, the Yew, 

 Juniper and Scots Pine; that of central and northern Europe includes 

 the same three with the addition of the Spruce and Silver .Firs, the 

 Larch and the Cembra and Mountain Pines; and if we add to this area 

 all Asia north of the Himalayan and Hindu-Koosh ranges, but excluding 

 China and Japan, only six more species are present of which the 



* .!. Starkit- Gardner, British Eocene Flora, Vol. II. pp. 20101. 

 * Sir A. Geikie, Text Book of Geology, ]>. 884. 



