OKLAHOMA ACADEMY OF SCIENCE 43 



Cretaceous, and having declined during Tertiary times, it was 

 repeating in its life history, nature's inexorable law, and slowly 

 but surely approaching the point of extermination. 



But the type still persists. Tenaceously it retains its grip on 

 life. Today but two species remain, Platanus oricntaJis, the 

 plane tree of Europe and Asia, and Platanus occidcntalis, the 

 North American sycamore or button wood. No longer the king 

 of the forest, abundant in species, widely distributed, strong hardy 

 vigorous, predominating over the dicotyledons of its time, the 

 modern decadent representative of the genus, clings to the water 

 courses, selecting with care its enviroment, and like an old man, 

 full of years, await with fortitude its inevitable destiny. 



LIFE ZONES AND ZONE INDICATORS IN 

 OKLAHOMA 



R. O. Whitenton, 1917. 



During the past summ.er (1917) it was my privilege to study 

 in detail the Life Zones and their indicators, in Colorado from 

 the Continental Divide to and including the plains of eastern Colo- 

 rado. The interest aroused in the subject led me to investigate 

 the zones and their indicators in Oklahoma. At present this in- 

 vestigation is far from complete and the conclusions reached are 

 necessarily rather general and subject to correction. But it is 

 my hope that others will take sufficient interest in the subject so 

 that enough data may be brought together to place the distribution 

 of animals and plants in the State on a scientific basis. 



Life Zones are trans-continental belts characterized by par- 

 ticular associations of animals and plants. According to Merriam. 

 "The northward distribution of terrestrial animals and plants is 

 governed by the sum of the positive temperatures (mean daily 

 temperature above 60°c.) for the entire season of growth and re- 

 production, and the southward distribution is governed by the 

 mean temperature of a brief period (about six weeks) of the 

 hottest part of the year. 



The zones outlined by Merriam seem to have more merit 

 than any classification brought to our attention. His seven zones 

 are : Artie, or Artie-Alpine, Tropical, the upper and lower Aus- 

 tral and upper and lower Sonoran respectively. 



In order to see the relations between the zones in Oklahoma and 

 those of the rest of North America we shall discuss the zones 



