REPORT OF EXECUTIVE COMMITTEE. lOI 



The work may be outlined as follows : 



(i) The amount of water in desert soils was determined by sam- 

 ples both after a long period of drought and after rains. The amount 

 of water at the dryest season, at no great depth, is surprisingly 

 great. After four to five weeks without rain the soil in the open- 

 ings between rock fragments, at a depth of 40 centimeters, was 

 found to contain water to the extent of 10 to 12 per cent by volume. 

 These observations were made on the shoulder of Tucson Mountain, 

 near the Desert Laboratory. 



(2) The retaining power of adobe clay for water was measured 

 and found to be 50 per cent by volume. 



(3) A piece of apparatus was devised to measure the natural 

 evaporation by short periods, and a curve was constructed for several 

 weeks. This rate was related to the loss by a free water surface, 

 soil of various degrees of moisture, sugar solutions, the leaves of 

 several desert plants, etc. 



(4) The sensible temperature was recorded by short periods for 

 several weeks. The importance of wind in lowering this and in 

 raising the rate of evaporation is emphasized by the results. 



(5) The amount of water necessary to promote germination in 

 several seeds was determined, as was also the degree of dryness 

 that could be withstood by several desert plants. 



(6) The concentration 6f the juices of several desert plants was 

 found to be little or no higher than that of ordinary plants. The 

 amount of mucilage in the sap may have to do with retaining the 

 water. Further experiments on the relation of mucilage to evapo- 

 ration of its solution will be carried out. 



(7) The resistance of soils of varying degrees of moisture to ab- 

 sorption by roots was determined by several methods, and this 

 reduced to terms of osmotic pressure. 



(8) The power of a soil to absorb water from a moist atmosphere 

 was measured in several cases. 



(9) The rate of transpiration of small plants (per unit leaf sur- 

 face) was determined during periods of several days, ending in the 

 wilting of the plant from lack of water. 



E. W. Olive, University of Wisconsin, Madison. Grant No. 132. 

 For researches on the cytology oj certain lower plants. ( First report 

 is in Year Book No. 2, p. xxvii.) $1,000. 



Abstract of Report. — Six distinct lines of research are in progress, 

 with a view of determining, if possible, the origin in the lower plants 

 of the complicated cell conditions found in the higher organisms. 



