386 



GEOGRAPHICAL DISTRIBUTION AND 



[Ch. XL. 



simply the modified descendants of such an older fauna and 

 flora as happened to preexist under " " -^-^ -••- 



a somewhat 



phase of the earth's physical geography, or they are the 



mean 



1 



each those lands. 



same 



maintain 



into com 



with species 



from 



w^ould never without the aid of man have come into contact 



with them. 



Marine 



[ants. — The vegetation of the sea, like that of the 

 land, is divisible into different provinces each inhabited by 

 distinct species, but these provinces are fewer in number 

 because the temperature of the ocean is more uniform than 

 that of the atmosphere, and because the area of 

 small proportion to that of water, so that the 

 marine plants is not so often stopped by barriers of land as is 

 that of the terrestrial species of the ocean. It is a remark- 

 able fact that Dr. Hooker has been able to identify no less 

 than a fifth part of the antarctic Algce, excluding the :N"ew 



mip-ration 



there is 



d Tasmanian groups, with British i 

 much smaller proportion of cosmo 



Yet 



among the Algse than amon 



gams 



Hepat 



quitous 



/ 



— The fact last alluded to, of the ubi- 



yptogam 



deserves special 



attention. Linnsens observed that, as the germs of plants of 



fa 



^ 



im 



difficulty 



being dispersed throughout the atmosphere, and carried to 

 every point of the globe, where there is a station fitted for 

 them. Lichens in particular ascend to great elevations, 



e times 



mean 



nearly at the freezing point. This elevated position must 

 contribute greatly to facilitate the dispersion of those buoy- 

 ant particles of which their fructification consists.^ 



p 



r 



* Linn., Tour in Lapland, vol. ii. p. 282. 



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