1915] 



SETCHELL DISTRIBUTION OP MARINE ALGAE 



291 



Considerable work has been done in the description of 

 various floristic associations occurring in various depth belts 

 and of various formations, and the special ecological relation- 





ships have been discussed and made reasonably plain. My 



intention, however, is to discuss the broader distribution and 

 segregation of floras, particularly as to regions and perhaps 

 provinces and to attempt to determine the factor, or factors, 

 governing these. 



In attempting to mark out the various floristic regions and 

 their provinces, we are met with certain difficulties. The 

 flora of the Arctic or Boreal region is fairly definite and has 

 been the most carefully studied and tabulated. The prov- 

 inces of the Arctic region are the Asiatic, the American, that 

 of West Greenland, and the extended province of Spitzbergen 



(cf. 



Simmons 



'05). The North Atlantic Ocean as distin- 



guished from the Arctic has five regions, viz., those of North- 

 western Europe, Southwestern Europe, and the Mediterraneo- 

 Northwest African region on the east and Northeastern North 

 America and Middle eastern North America on the west. The 

 Antarctic or Austral region possesses a fairly consistent flora 

 and is not so readily divided into provinces, but the Antarctic- 

 Magellanic province may be contrasted with the Indo-Pacific 

 province. The South Atlantic Ocean has a flora as yet little 

 understood, but, for the present at least, may be considered 

 to have the regions of Southwest Africa and Southeast South 

 America. The Northern Pacific has Bering Sea probably 

 representing a province of the Arctic or Boreal region. 

 Otherwise it is divided into five regions, viz., those of North- 

 west North America, Middle "West North America, and South- 

 west North America on the east and the Ochotsk-Yeso region 

 and that of East and West Honshu (or Nippon) on the west 



shores. The South Pacific Ocean has five regions, viz., those 

 of Southwest South America, Middle West South America 

 on the east and those of New Zealand and South and South- 

 east Australia on the west coasts. The southern portion of 

 the Indian Ocean has two regions, viz., that of Southwest 

 Australia and the South Africa or Cape region. The tropical 

 waters may probably be divided into two regions, viz., the 



