March 2, 1917] 



SCIENCE 



201 



of those common to two or more subdivi- 

 sions and lay particular stress on the rela- 

 tive number of species to the genus in the 

 various geographical divisions or subdi- 

 visions. 



The results of this purely floristic work 

 on the marine algffi has been, just as has 

 happened more extensively in phsenogamic 

 floristics, the separation of floras more or 

 less distinctly marked off from one another 

 and in some cases the discovery of definite 

 demarcation points. As illustrations of 

 this may be mentioned the following: the 

 Arctic and Mediterranean marine floras 

 were readily understood, but the intermedi- 

 ate floras were not distinguished, nor were 

 there any sharp points or districts of de- 

 marcation discovered. The marine flora of 

 the Cape of Good Hope region has always 

 been recognized as very distinct, but the 

 exact limits have never been determined. 

 On the eastern coast of North America, on 

 the contrary, and especially on the coast, of 

 New England, not only was the northern 

 flora recognized as different from that of 

 Long Island Sound and southward, but also 

 the .Cape Cod Peninsula was indicated as 

 the region of demarcation between the two. 

 This was first mentioned by W. H. Harvey 

 in the first part of the "Nereis Boreali- 

 Americana" (1851). Harvey divides the 

 east coast of North America into 4 divisions, 

 viz., "First, the coast north of Cape Cod, 

 extending probably to Greenland; second. 

 Long Island Sound, including under this 

 head New York Harbor and the sands of 

 New Jersey; third. Cape Hatteras to Cape 

 Florida;" and "fourth, Florida Keys and 

 shores of the Mexican Gulf." This divid- 

 ing up of the marine flora of the eastern 

 coast of North America is the first division 

 of any definiteness for that of any extended 

 coast and corresponds fairly closely to the 

 zones of the marine flora into which my own 

 investigations indicate it should be divided. 

 Harvey's statements in the "Nereis Bo- 



reali- Americana " result from his ideas 

 formulated in the second edition of his 

 "Manual of the British Marine Algse" and 

 are a direct application of the earlier ideas 

 of Lamouroux (1825, 1826). Along with 

 the separation of floras is a comparison, as 

 to similar latitudes and isothermal lines, 

 between the east coast of North America 

 and the coasts of Europe, but these iso- 

 therms are lines of mean annual tempera- 

 ture and likewise are those of the air, but 

 not of the water, indeed for application to 

 land floras, and not affecting, as a whole, 

 at least, the marine flora. This work of 

 Harvey was the first detailed attempt to 

 associate floristic methods with the factors 

 which control climatic distribution. 



Later developments of the floristic idea 

 are to be found in Kjellman's work, espe- 

 cially in the "Algas of the Arctic Sea" 

 (1883) and in the works of Simmons 

 (1897) and of Borgesen and Jonsson 

 (1905) on the marine flora of the Faeroes 

 and the North Atlantic. The Baltic Sea 

 was studied as to its marine flora by Reinke 

 (1889), Svedelius (1901), and Kylin 

 (1906, 1907), that of New England by Far- 

 low (1881) and Collins (1900), that of Ice- 

 land by Jonsson (1912), tropical floras of 

 the Indian and Pacific Oceans by Schmitz 

 (1896) and Schroeder (1902), and the ant- 

 arctic floras by Gain (1912). All these 

 works have been along the same general 

 lines. 



To sum up the results of the floristic 

 work, general climatic regions have been 

 set off and distinguished from one another, 

 methods of and agents in dispersal have 

 been discussed, demarcation points between 

 floras have been determined, centers of dis- 

 tribution have been emphasized, and bar- 

 riers to dispersal have been surmised. All 

 these lead toward the discussion of climatic 

 distribution and to some extent toward that 

 of topographical distribution or ecology. 

 Yet these are all more floristic in style and 



