OF THE BEIXISn PLOEA. 



137 



2. The three " Classes" are generally distributed, and tlie larger 

 " Orders " also. 



3. The least complex are most widely diffused. 



4. " llepresentative " forms occur under similar but separated 

 conditions. 



5. Every country has a different flora. 



6. Exuberance decreases from the Equator to the Poles. 



7. Uniformity in numbers and luxuriance mark some countries ; 

 great variability, others. 



8. The Arctic (Scandinavian) flora is the only one found on 

 temperate and tropical mountains as well as in the extra- tropical 

 southern hemisphere. 



9. Insular floras (Oceanic) are peculiar. 



10. Naturalised plants increase in proportion as they are trees, 

 shrubs, perennials, or annuals. 



1 1 . The causes of distribution are changes of climate, as also of 

 land and sea. 



Having now considered the present distribution of the British 

 Flora, we have to account for it as far as possible ; and here theory 

 must supplement facts. In looking back to discover a historical or 

 rather geological origin of our present flora, we soon find that there 

 have been very remarkable changes in the characters of successive 

 floras that peopled our country. Going no further back than the 

 Eocene period — for attempts at deductions as to climatal conditions 

 become more and more uncertain in proportion as the ftiunaj and 

 florae are more remote in time from and unlike their living repre- 

 sentatives — we find tolerably certain evidence that the climate of 

 England at that time was tropical, at least so far as palms, Mimoste, 

 Nipadites, on the one hand, and turtles, crocodiles, and large water 

 snakes on the other, justify us in drawing such a conclusion. This 

 period, then, could not have seen the origin of our present 

 temperate and arctic floras. The next epoch, the Miocene, like- 

 wise fails to furnish any members of it. The flora of this period 

 was subtropical, but probably became less and less so as the next 

 — the Pliocene epoch — drew near. The Miocene flora is remark- 

 able for its great extent. Not only are remains of plants to be 

 found in England, as at Bovey Tracey in Devonshire, but at many 

 places on the Continent ; and what is still more remarkable, it is 

 found to have extended all over the Arctic regions — as at Disco 

 Island, Greenland, arctic North America, etc. In all these places 

 such plants as vines, custard apples, figs, cinnamons, Nelumhimn (the 

 lotus of the East), water-lilies, and the ubiquitous " JFeUingtonia"* 

 are to be found. This shows, therefore, that there must have been 

 a very different state of things in the Northern hemisphere then 

 from what obtains now. The preceding flora had its day, flourished, 

 and then passed away for ever. A colder period drew on. This 



* This genus is better known to botanists as Sequoia, and the species S. 

 Conttsia; is found at Bovey Tracey ; two species only now exist, S, sempervirens 

 (red-wood) and S. yiyanlea, both confined to California. 



