ECOLOGY — GEOLOGY. 297 



stations. Indeed, it has been the chief factor in bringing about a 

 reaHzation of the imperative needs of the grazing industry in the 

 present emergency. In the course of the work, all but 3 of the 15 

 experiment stations have been \dsited, while grazing experiments 

 have been started or planned at each of these. Inclosures for the study 

 of carrying capacity under complete protection, as well as in areas 

 where rodents are eradicated, have been established in several States, 

 and it is hoped to install them in practically all. Several months have 

 been devoted to a grazing reconnaissance which has covered 12 States 

 and has permitted a careful comparison of grazing conditions in them. 



Rubber Plants, by H. M. Hall and Frances Long. 



An extensive survey of the Great Basin region for rubber-producing 

 plants was begun in 1917 as a w^ar-emergency project. During 1918 

 this has broadened into a comprehensive search throughout the West 

 for all species known or suspected to contain rubber. It is proposed 

 to continue this work as a far-reaching piece of research to determine 

 all the possibilities of rubber production in the West, from native 

 plants at least. A small chemical laboratory was fitted up at the 

 Alpine Laboratory for the grinding and extraction of the plant material 

 during the summer, and later analyses were made at the University 

 of California and the Desert Laboratory. In addition to species of 

 Chrysothamnus and Ericameria studied previously, 18 genera and 30 

 species have been examined chemically. These were largely latex 

 plants, though a number were composites related to genera known to 

 contain rubber. In most cases, the leaves and stems were analyzed 

 separately. Rubber was found in 25 of the species examined, but in 

 most it was in too minute a quantity to be of importance. In 11 

 species, however, the percentage was sufficiently high to justify further 

 investigation, and in 4 of them it was high enough to warrant the hope 

 that the species may serve for the production of rubber on a com- 

 mercial scale. 



GEOLOGY. 



Chamberlin, T. C, University of Chicago, Chicago, Illinois. Study of fun- 

 damental problems of geology. (For previous reports see Year Books 

 Nos. 2-16.) 



The work of the year has followed three closely related lines: (1) 

 a study of cosmic units as such with a \'iew to bringing out, for 

 comparative use, such common properties as are essential to their 

 organization; (2) the development of modes of using these common 

 properties in concrete questions of cosmic evolution in fields where 

 other lines of treatment are not now available; (3) continuation of pre- 

 vious inquiry into certain factors of geologic climate which have come 

 to be entangled with the broader issues of cosmic evolution. 



