ECOLOGY. 359 



back 3,300 years. This is intended not merely as a standard to which 

 all Sequoia cui^ves may be referred, but also as a basis for checking and 

 cross-identifying the results from trees of adjacent regions. Much 

 progress has been made in the improvement of the periodograph, and 

 it will be soon available for much readier and more accurate analysis 

 of both old and new curves. The annual rings of cores taken from the 

 pueblo ruins at Aztec, New Mexico, have been studied with special 

 reference to the possibility of dating the ruins and obtaining the rela- 

 tive age of the different portions. It has been possible to do this, and 

 it is hoped that the method of cross-identification will yield the dates 

 of the actual construction. A considerable number of cores have been 

 obtained from several species at the Alpine Laboratory with the object 

 of determining the effect of slope-exposure on the growth of annual 

 rings. A journey has been made to the Miocene fossil forests of Flor- 

 issant and Yellowstone Park and to the Eocene forests at Medora, 

 North Dakota, for the purpose of studying the rings of the fossil trees 

 in relation to climatic cycles of the past. Since complete sections are 

 practically impossible, it is hoped to construct such in so far as possible 

 by means of photographs, tracings, and fragments. 



An extensive study has been made of the relation of drought periods 

 to climatic cycles throughout the West. In addition to the 17 western 

 States, an analysis has been made of the weather records of Indiana, 

 Illinois, Wisconsin, Minnesota, Iowa, and Missouri. The annual excess 

 or deficit in rainfall has been tabulated for each State for 8 periods of 

 5 years each, centering on the sun-spot maxima of 1837, 1848, 1860, 

 1870, 1883, 1893, 1907, and 1917. The results show not only that 

 every State has had from 2 to 4 years of critical drought at the most in- 

 tense sun-spot maxima, but this is also fully disclosed in the totals for 

 the entire region. For purposes of comparison, a study is likewise 

 being made of the relation between sun-spot maxima and rainfall in 

 other arid regions, such as Argentina and South Africa. 



Permanent Quadrats, by F. E. Clements, E. S. Clements, and G. V. Loftfield. 



The use of permanent quadrats for the study of changes in vegetation 

 and of the competition of dominants and of subdominants has now been 

 extended to the majority of the plant associations of the West. The 

 total number is about 200. In connection with the transplant areas, 

 they are used to follow the course of ecesis in detail, as well as for de- 

 termining the total production in native as well as culture vegetation. 

 Such clip quadrats have also been employed in connection with the ro- 

 dent exclosures in Arizona. Quadrats have also been established for 

 the purpose of tracing periodicity in vegetation, and they are especially 

 important in following the alternation of annual-perennip species 

 where the identity of each individual must be beyond question. A 

 new type of permanent quadrat has been estabUshed in the basic quad- 



