into the Himalaya. Sequoia and Carya inhabit the uplands of west and east North 

 America respectively. 



Still other noteworthy facts that have appeared are: — That the number of trees 

 and shrubs in the Reuverian flora was probably much greater, both absolutely and 

 proportionally, than it is in the Central European flora of today; and that the flora 

 was probably much richer in species. The actual number of species obtained is very 

 great, as compared with other Pliocene strata; and the deposits are by no means ex* 

 hausted, for each fresh consignment of material added a number of new forms. The 

 flora too must have been very varied, for numbers of the species are represented by but 

 one specimen. Taking these facts into consideration, together with the correlative fact 

 that it is but a very small fraction of any flora that can be preserved through long ages 

 in a state of fossilization, we realize what an enormous flora the Reuverian must have 

 been. It was possibly in some degree comparable in variety, in the number of its species, 

 and in the abundance of its trees and shrubs, with the present*day flora of Western 

 China. It is here worth noticing that the proportion of trees and shrubs obtained in 

 three similar deposits, belonging to three successive periods, the Reuverian, the Teglian, 

 and the Cromerian, falls from 50 per cent, of the whole determined flora in the Reuver* 

 ian, to 24 per cent, in the Teglian, and 15 per cent, in the Cromerian. Bearing in mind 

 also that as a general rule trees and shrubs are large*fruited and large*seeded, and her* 

 baceous plants small*seeded, we see that it is among the large*seeded plants that the 

 greatest proportional (we do not say numerical) extermination took place. 



We must now consider what these facts imply. It can hardly be doubted that 

 the alliances shown by the Reuverian fossils, and the known connexion between the 

 Chinese and North American floras (Asa Gray, Wilson, Sargent), indicate three great 

 streams of migration, radiating from some common centre in the north, and directed 

 towards warmer climates. Two of these streams of migrants effected (more or less com* 

 pletely) their escape to congenial latitudes. The American found its way directly open 

 to the tropics. The East Asian, by way of the coastal plains of China, and the great 

 valley systems of that country, ultimately reached warm temperate and subtropical 

 regions. Hence one cause of the great wealth of species in these countries at the present' 

 day. For this migration was not a series of isolated episodes; it was rather, a continuous 

 movement of successively cooler floras, following one another southward, till/the 

 direction of the migration was reserved by the reversal of the climatic conditions, diuring 

 the first Interglacial Period. But every wave of this migration brought its qubta of 

 species to enrich the flora of China, and in the earlier periods, of North Amerj/ca also. 



It would appear that the third stream of migrants, that which entered' Europe, 

 the existence of which is proved by the Reuverian fossils, was less fortunate. Driven 

 southward by the ever*advancing cold, by no route could it unimpeded reach climates 

 more genial than were offered by the Caucasus, and the south of France. Throughout 

 the whole length of Europe and Asia, till the coastal plains of China were reached, 

 the retreat to the south was cut off by one unbroken barrier of seas, deserts, and moun* 



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