386 THE AMERICAN NATURALIST [Vol. LIV 



toward solutions of the problems of distribution, are 

 founded more particularly on the influence and control 

 of distribution by edaphic factors, or those more particu- 

 larly connected with the substratum and concerned in 

 the studies of association and formations, in other words 

 having to do particularly with topographic distribution 

 as contrasted with climatic distribution. 



Humboldt's publications concerned themselves partic- 

 ularly with climatic distribution, although, incidentally, 

 he necessarily touched upon topographical distribution. 

 The chief factor of control in climatic distribution recog- 

 nized by Humboldt and his successors is temperature, 

 and Humboldt called attention, in most graphic ways, to 

 the resemblances between the climatic zones of latitude 

 over the earth's surface and those of altitude passed 

 through in the ascent from sea-level to thousands of 

 meters above it. Those of us who are older remember 

 the reproductions of Humboldt's diagrams of the various 

 zones (or perhaps better, belts) of vegetation of moun- 

 tain peaks situate in different latitudinal zones which 

 were reproduced in the various atlases and older geog- 

 raphies. Lamouroux, in 1825 and 1826, applied the gen- 

 eral principles of Humboldt, DeCandolle and Kobert 

 Brown, to marine plants, especially to the algae, and dis- 

 tinguished latitudinal zones and differences of distribu- 

 tion in depth (belts), as well as the effect of certain fac- 

 tors on topographical distribution. Lamouroux was 

 followed by Greville and Harvey in the attempts to dis- 

 cuss the distribution of marine algae and the latter (1852) 

 divided the Atlantic coast of North America into 4 divi- 

 sions and emphasized the position of Cape Cod as a de- 

 marcation point. These authors and their ideas may be 

 taken as starting points of the discussions more or less 

 contemporaneous and later. 



A definite attempt to determine the criteria of a cli- 

 matic zone was made by C. Hart Merriam (1894, 1898) 

 in his papers on " life-zones" and "crop-zones" of the 

 United States. Merriam used summation indices com- 

 piled for a large number of stations and divided the 



