ECOLOGY. 287 



ECOLOGY. 



Clements, F. E., Tucson, Arizona. Associate in Ecology. (For previous re- 

 port see Year Book No. 16.) 



The experimental work of the year has been centered at the Alpine 

 Laboratory on Pike's Peak during the summer. Experiments have 

 also been made at the Desert Laboratory from January to May upon 

 the periodicity of stomata and their relation to transpiration and 

 witing. Vegetation studies have been carried on throughout both 

 thelse periods in the region about Colorado Springs and Tucson re- 

 spectively. In addition, two major expeditions have covered a large 

 part of the West in connection with the further investigation of indi- 

 cator plants and grazing conditions. The first of these traversed 

 Arizona, California, Oregon, Idaho, Utah, Wyoming, and Colorado 

 during May and June; the second occupied the month of September 

 and was concerned chiefly with the Great Plains from Colorado to 

 North Dakota and thence southward through South Dakota, Nebraska, 

 Kansas, Texas, and New Mexico to Arizona. 



In both experimental and vegetation work, the principles of syn- 

 thetic ecology have served as a guide. The chief emphasis has been 

 placed upon quantitative measurements and the correlation of fac- 

 tors and responses, both with plants in communities and with indi- 

 viduals. An especial effort has been made to correlate the various 

 researches with each other and to synthesize the results in such a 

 manner as to permit their application to related fields. It has also 

 been recognized for the first time that animals are a factor of pro- 

 found importance in all plant associations and a number of quadrat 

 inclosures and exclosures have been installed to measure their effects. 

 The studies at the Alpine Laboratory have been largely in continua- 

 tion of researches carried on during the past fifteen years, as a con- 

 sequence of which it has proved possible to complete several of them 

 for publication. Owing to the exigencies of the situation, the major 

 attention during the year has been given to plant indicators, climatic 

 cycles, and grazing research. This has made it necessary to further 

 postpone the completion of the study of succession and reclamation 

 in bad lands. However, opportunity has been found for visiting 

 several new bad-land areas in connection with the work on indicators 

 and climatic cycles. It has also proved possible to organize the work 

 in paleo-ecology with greater definiteness. 



Factor Stations. 



As a basis for the interpretation of plant responses and community 

 behavior, a number of stations has been established at Pike's Peak 

 in different formations and at different altitudes. These have been 

 located on the plains, in the foothills, and in the montane and subal- 



