DEPARTMENT OF BOTANICAL RESEARCH. 69 



The Cactacecc.—'Vht facilities of the Desert Laboratory were granted to 

 Dr. J. N. Rose, of the Smithsonian Institution, for an investigation of the 

 Cactacese of southern Arizona. In accordance with this arrangement trans- 

 portation and field equipment were furnished Dr. Rose during April and 

 May, by which he was able to make explorations, collections, and field obser- 

 vations in western Texas, New Mexico, Arizona, and southern California. 

 A large amount of material was secured by which many questions as to habit 

 and relationship in this important group may be answered. 



The Geology of the Tucson Region. — Dr. W. P. Blake, Territorial geolo- 

 gist of Arizona, by special request, has compiled the results of his observa- 

 tions on the physiography and geology of the Tucson region during the last 

 18 years. This material constitutes a special section of publication 99, re- 

 cently issued. The treatment of such phases of the subject as the origin of 

 the slopes, soils, former lacustrine conditions, changes in climate, submer- 

 gence, and elevation, together with the map of the region during the Post- 

 pliocene period, makes this contribution of great and enduring value to 

 workers in all branches of natural history, as well as being of great popular 

 interest. An area of nearly 2,000 square miles is critically treated in this 

 paper. 



Heredity in the Chrysomclid Beetles. — Dr. W. L. Tower, in the continua- 

 tion of his extensive researches on the influence of climatic factors upon the 

 organic processes most directly concerned in the evolution of organisms, 

 which have been carried on in Mexico for several years, has placed a series 

 of cultures at the Desert Laboratory. The conditions here afford oppor- 

 tunities for testing the total effect of the factors of the Tucson desert upon 

 organisms from a widely distant locality, and of analyzing these effects. 



Two series of experiments were begun in the current year for obtaining 

 evidence upon problems as follows : 



(i) The action of the combined physical environment upon organisms 

 that are transported into an entirely new habitat and removed from the 

 organic factors, such as the food and organic enemies questions. Four differ- 

 ent series of cultures were started under this general head and three of them 

 have thus far succeeded beyond the fondest expectations, while one failed 

 entirely. 



(2) The action of changed physical conditions of existence upon particu- 

 lar organic processes that are of importance in evolution. Under this head 

 one set of experiments was started in June and has thus far given every 

 promise of exact and conclusive data upon the problems under consideration. 



Vivaria inclosed by close-meshed wire-netting have been constructed, in 

 which the natural food plants and pure strains of beetles have been placed. 



