March 2, 1917] 



SCIENCE 



203 



chemical aspects as well as the modes of 

 attachment to and the various methods of 

 aggreg'ation of the algffi on it. He consid- 

 ers also the aspects of chemical composition 

 and variation in salinity of the sea water, 

 as well as its purity, its gas content, its 

 density and its color. There follows a dis- 

 cussion of the influence of the temperature 

 of the water, of the influence of light, of 

 color of the water, of methods of dispersal 

 by currents and by fishes, of the nature of 

 spores, etc. Finally the general organiza- 

 tion of the plants themselves is dealt with. 



Under the head of climatic distribution 

 and with the controlling factor of tempera- 

 ture in mind, may be mentioned my own 

 papers on this subject in 1893, 1903 and 

 1914, respectively, where there is an at- 

 tempt made to outline certain climatic zones 

 depending primarily upon the mean tem- 

 perature of the surface waters. In these 

 papers I have treated in a general and 

 preliminary way of temperature zones, 5° 

 C. apart, as to surface waters and mean 

 maximum temperature. I have also briefly 

 touched upon the invasions of these zones 

 at seasons of other temperatures, particu- 

 larly at the mean minima, by species from 

 other zones. These invasions account for 

 much of the seeming disturbances of uni- 

 formity and exclusiveness of flora. I am 

 now prepared to account for other inva- 

 sions due to the raising of temperature of 

 the algEe in tidal belts and in shallow areas, 

 such as salt lagoons and estuaries through 

 the temperature of the air. Through these 

 factors practically all invasions or over- 

 lappings from one zone into another, may, 

 as it now seems to me, be explained. 



Turning from the papers which are gen- 

 erally floristie or which deal only with the 

 general climatic factors, there are certain 

 papers dealing with the topographical or 

 ecological distribution. While Lamouroux 

 hinted at certain features such as the in- 

 fluence of aeration in the tidal belts and 



the influence of the substratum, the first 

 papers to deal with topographical features 

 of distribution for marine algee were those 

 of J. G. Agardh (1836) and Oersted 

 (1844) . Both divided the shore belts of the 

 Danish and southwest Swedish coasts into 

 three regions, the uppermost characterized 

 by a predominance of the green algffi, the 

 middle by the predominance of brown 

 algffl, and the lowermost by that of the red 

 algffi. Oersted, however, was the first to 

 attribute this division into regions to a defi- 

 nite influence, viz., to the light as to depth 

 penetration and as to color. Kjellman, 

 later and in several papers, also divides the 

 shores generally into three "regions," the 

 littoral, the sublittoral and the elittoral. 

 He also developed the idea of algal forma- 

 tions, or, as they are more properly called, 

 of "associations." In both these segrega- 

 tions, Kjellman is followed by most later 

 writers. 



Eosenvinge for Greenland, Boergesen for 

 the Faeroes, Kylin for the western coast of 

 Sweden and Jonsson for Iceland have ap- 

 plied and extended the ideas of Kjellman 

 as to topographical units and the factors 

 controlling them, as well as for factors of 

 climatic importance. Jonsson (1912) has 

 given a particularly complete and satisfac- 

 tory outline and discussion. 



Schimper, Warming and Clements have 

 given classifications of the marine, as well 

 as the fresh-water alga, distinguishing the 

 plankton or swimming forms from the 

 benthos, or attached forms, and, in distin- 

 guishing the benthos foi-mations according 

 to the substratum, viz., as to sand or rock 

 and in making even farther distinctions. 



Two papers of recent date contain data 

 and observations of great importance in 

 topographical distribution of the marine 

 algffl. One of these is the contribution of 

 B. M. Davis (1913) to the "Biological Sur- 

 vey of the Waters of Woods Hole and Vi- 

 cinity," while the other is the paper of K. 



