REPORT OF THE PRESIDENT, I9IO. 21 



problems whose solution requires aid from many sciences other than those 

 which are commonly held to make up biology, and especially from chemistry, 

 physics, and meteorology. Thus the researches of this department call for 

 much collaboration and for a wide range of observation, experiment, and 

 determinate analysis. 



During the year the Director of the department has continued his inves- 

 tigations on the water-balance of succulent plants, on the conditions of 

 vegetable parasitism, on the variability in plant species induced by chemical 

 treatment of their seeds, and on the influences of climate on plant organisms. 

 In collaboration with Prof. Ellsworth Huntington, research associate of the 

 department during a portion of the year, the Director has begun a general 

 climatological study of the region about Tucson, giving special attention to 

 the factors and effects of the Santa Cruz and Asuncion river systems. 



Dr. Cannon, of the permanent departmental staff, has given attention espe- 

 cially to his elaborate investigation of the root systems and habits of desert 

 plants. For the purpose of extending the range of his studies in this funda- 

 mental subject he visited the Sahara Desert and will spend most of the year 

 in that advantageous field for both comparativ and direct observations. Some 

 of the more important conclusions alredy establisht in respect to this inquiry 

 are set forth in the Director's current report. 



Dr. Shreve, also of the permanent staff of the department, while occupied 

 with the more general problem of the relation of plants to climate in the 

 United States, has also carried on special investigations of the vital statistics 

 of plants in the vicinity of the Desert Laboratory; of the vegetation in the 

 Santa Catalina Mountains ; and of the physiological characteristics of the 

 lace-fern family of plants. In the first of these researches he has been aided 

 by the collaboration of Dr. Livingston, who resignd from the staff of the 

 department a year ago to accept a professorship in Johns Hopkins University. 



Observations on the phenomena presented in the drying up of Salton Sea, 

 and especially on the influx of vegetation over the bared strands and islands 

 of this slowly retreating body of water, have been continued during the year. 

 In this work a series of soil analyses of the strands has been secured thru the 

 cooperation of Mr. E. E. Free, of the Bureau of Soils of the U. S. Depart- 

 ment of Agriculture. 



Publications by members of the department issued during the year are 

 shown in the list on pp. 32-33 and in the bibliography of the Year Book. 

 Others in press are Nos. 131, 139, 141. One of these, No. 139, on the 

 Guayule, a desert rubber-producing plant of considerable economic impor- 

 tance, is the work of Prof. Francis E. Lloyd, formerly a resident associate 

 of the department, but now a member of the faculty of Alabama Polytechnic 

 Institute. 



