ECOLOGY. 331 



Synthetic methods and principles have again been employed in the 

 correlation of factor measurements, physiologic responses, and com- 

 munity behavior. Especial emphasis has been placed upon securing 

 objective results in the case of both the individual plant and the plant 

 community. As a consequence, new methods have been devised for 

 using plants as measures or indicators, and for obtaining the decision 

 of the plant where the historical and physical factors in vegetation are 

 more or less confused, as is usually the case. This has led to an inten- 

 sive study of animal effects and correlations in the plant community, 

 and to the important conclusion that no vegetation is natural in the 

 sense of being wholly undisturbed. In grassland at least, the line 

 between natural and artificial conditions completely disappears as a 

 result of the study of grazing by cattle and by buffalo. 



Factor Stations. 



In addition to the stations maintained last year on the plains and in 

 the montane zone at Pike's Peak, a third station has been installed in 

 the subalpine zone. This series comprises three climaxes, mixed 

 prairie at 6,000 feet, montane Douglas fir at 9,000 feet, and subalpine 

 Engelmann spruce at 1 1 ,000 feet. A second series is devoted to the serai 

 communities at 8,500 feet, ranging from gravel-slide to chaparral and 

 pine forest. Factor stations have also been maintained in the sandhills 

 at Central City, Nebraska, and in the true prairie at Lincoln, Nebraska, 

 with substations in low and high prairie. These were all similarly 

 equipped with instruments for factor readings, but only the stations 

 at Pike's Peak possessed phytometers as well. Attention was centered 

 upon the water relations, water-content, humidity, and evaporation, as 

 temperature appeared to exert only indirect effects, except in growth. 

 At Pike's Peak the factor results were utilized chiefly in connection 

 with the use of phytometers and the quadrat-transect series. In the 

 grassland formation of Nebraska and Colorado, they were employed 

 primarily in root studies and in the transplant quadrats. Since they 

 are basic to practically all the studies, instrumental methods will be 

 continued and expanded from year to year in correlation with phyto- 

 meter processes and quadrat installation. 



The Phytometer Method, hy F. E. Clements, J. E. Weaver, and 

 G. W. Goldsmith. 



The use of standard plants to measure habitats in terms of plant 

 response and growth has been extended to include a climax and a serai 

 group of stations. The former consists of mixed prairie, montane for- 

 est, and subalpine forest at altitudes of 6,000, 8,500, and 11,000 feet 

 respectively. The successional series lies in the montane forest, and 

 consists of seven stations, namely, gravel-slide, half-gravel-slide, 

 brook-bank, grassland, thicket, pine forest, and Douglas fir forest. The 

 base station of the chmax series is also located in the half-gravel-slide, 



