294 CARNEGIE INSTITUTION OF WASHINGTON. 



(7) use of wire cages to confine pollinators to certain plants or species. 

 The results obtained have thrown much light upon the actual functions 

 of flower parts and have furnished a large amount of interesting 

 material on the habits and individuality of insects in particular. 



Field and Garden Study of Genera and Species, by F. E. Clements and 



H. M. Hall 



A general investigation of taxonomic criteria has been under way in 

 the Rocky Mountain region for a number of years, and more definite 

 studies on the Madiese in field and garden have been carried on for 

 a similar period. During the present summer, several important and 

 widely distributed genera have been made the subject of a special 

 inquiry into criteria and their application to the problems of distin- 

 guishing species from such minor units as varieties, ecads, mutants, 

 elementary species, etc. The genera selected were Chrysothamnus, 

 Artemisia, Atriplex, and Haplopappus. In the latter, a large number of 

 generic segregates have been recognized by recent authors, and hence 

 generic as well as specific criteria are here concerned. The field study 

 of the variants has reached the point where it has proved possible to 

 make a working outHne for the species and to relate the various segre- 

 gates provisionally to them. This constitutes the basis for the applica- 

 tion of statistical and experimental methods by which it is hoped to 

 outline a synthetic system based upon evolution and relationship. 

 This should not only permit the grouping of segregates of all sorts 

 about the proper parent species, but should also determine the nature 

 of the minor unit, whether variant, ecad, mutant, etc. At the same 

 time, it is proposed to furnish a convenient and accurate way of des- 

 ignating species and their minor units. 



Climax Formations, by F. E. Clements. 



In accordance with the general plan for making the knowledge of 

 the vegetation of the West available as rapidly as possible, much 

 attention has been paid to climax formations and their successional 

 development. The major attention has been given to the formations 

 of widest extent, such as grassland, sagebrush, mesquite, and chap- 

 arral, but all have been studied to some degree with one or two excep- 

 tions. In this connection all the States west of the Missouri River 

 have been traversed by automobile, with the exception of Montana 

 and Nevada. From 1913 to the present time, all of the 16 Western 

 States have been repeatedly crossed and recrossed in the investigation 

 of climaxes and succession. As a consequence, it has been possible 

 to recognize and delimit the various associations of the 9 climaxes 

 for the first time and to point out their relationships to each other, as 

 well as to the associations of adjacent formations. It has also per- 

 mitted the drawing of more definite distinctions between climax and 



