148 ZONATION 



representative species. His conclusion was that tempera- 

 ture is the principal cause of zonation upon mountains, and 

 that dryness and insolation are secondary causes. Kabsch 

 (J855:303) distinguished twelve zones of vegetation, corres- 

 ponding exactly to the temperature zones of the earth, and 

 recognised eight regions in altitude, designatng them accord- 

 ing to the type of vegetation. Engler (1879:334) used the 

 term zone for the primary divisions of provinces : these do 

 not correspond to vegetation zones, but represent zonally 

 disposed regions or districts for the most part. Grisebach 

 (i872:t29) established continental zones upon the basis of 

 dominant trees. Koppen (J884:2I5) laid down the principle 

 that the influence of temperature upon vegetation is best 

 measured by the length of the period in which the tempera- 

 ture lies between certain limits. On this basis, he proposed 

 the following zones: 1, tropical zone, temperature above 

 20° C. for all months; 2, subtropical zones, above 20° C. for 

 4-11 months; 3, temperate zones, a, constantly temperate, b, 

 summers hot, c, summers temperate, winters cold; 4, cold 

 zones, temperate for 1-4 months, the other months cold ; 5, 

 polar zones, below 10° C. for all months. Drude (1887:3) 

 characterised and charted tne following zones of vegetation : 

 1, nOrdliche glacial zone ; 2, nOrdliche winterkalte zone ; 8, 

 nOrdliche sommerheisse zone; 4, tropen zone; 5, sudliche 

 sommerheisse und gemassigte zone ; 6, sudliche kalte zone. 

 Raunkiaef (1889) noted the zonal arrangement of subform- 

 ations in the dune valleys of Jutland, where, in passing 

 from the dry margin of the valley to the moist center, the 

 following plants appear in zones: Galluna vulgaris. Erica 

 tetralios, Myrica gale, and Aira uliginosa. Magnin (1893:241,303) 

 gave a new trend to the study of zones by his thorough 

 investigation of the zonation of the Jura lakes. He found 

 that the majority of these lakes regularly show the same 

 series of zones: 1, a literal zone of amphibious plants, 

 Phragmites, Scirpus; 2, an interior zone of floating plants, 

 Nuphar; 3, a central zone of floating or somewhat submerged 

 plants, Potamogeton ; 4, a center of clear water, where Cera- 

 tophyllum, Naias, Ghara, Mtella, etc., grow submerged. 



