THE GENESIS AND MIGRATIONS OF PLANTS 223 



Port McNeil in the north of Vancouver Island, which is as 

 large as that of the modern species, and very similar in form. 

 Thus this beautiful vegetable type culminated long geological 

 ages ago, and was represented by many species, no doubt occu- 

 pying a prominent place in the forests of the northern hemi- 

 sphere. To-day only a single species exists, in our warmer re- 

 gions, to keep up the memory of this almost perished genus ; 

 but that species is one of our most beautiful trees. 



The history of the Sequoias or giant Cypresses, of which two 

 species now exist in limited areas in California, is still more 

 striking. These giant trees, monsters of the vegetable king- 

 dom, are, strange to say, very limited in their geographical 

 range. The greater of the two, Sequoia gigantea, the giant 

 tree par excellence, seems limited to a few groves in California. 

 At first sight this strikes us as anomalous, especially as we find 

 that the tree will grow somewhat widely both in Europe and 

 America when its seeds are sown in suitable soil. The mystery 

 is solved when we learn that the two existing species are but 

 survivors of a genus once diffused over the whole northern 

 hemisphere, and represented by many species, constituting, 

 in the Later Cretaceous and Eocene ages, vast and dark forests 

 extending over enormous areas of our continents, and forming 

 much of the material of the thick and widely distributed 

 Lignite beds of North-western America. Thus the genus has 

 had its time of expansion and prevalence, and is now prob- 

 ably verging on extinction, not because there are not suitable 

 habitats, but either because it is now old and moribund, or 

 because other and newer forms have now a preference in the 

 existing conditions of existence. 



The Plane trees, the Sassafras, the curious Ginkgo tree or 

 fern-leaved yew of Japan, are cases of similar decadence of 

 genera once represented by many species, while other trees, like 

 the Willows and Poplars, the Maples, the Birches, the Oaks 

 and the Pines, though of old date, are still as abundant as 



s. E. 16 



