62 REPORTS OF INVESTIGATIONS AND PROJECTS. 



The conditions mentioned result in a slow rate of growth in seed plants. 

 The ferns, however, are able to maintain rapid rates of growth, and display 

 transpiratory behavior of a different character. 



The Distribution and Movements of Desert Plants (by Dr. V. M. Spalding) : 

 The studies of Prof. V. M. Spalding on the distribution and movement of 

 desert plants have recently appeared in publication No. 113 of the Carnegie 

 Institution of Washington. In course of its preparation local and compara- 

 tive studies were conducted in various parts of the southwestern United 

 States, which have been reported in part in the Plant World and elsewhere. 

 The journal named has come under the editorial direction of Professor 

 Spalding and, in addition to much other material, has been made to include 

 contributions covering a wide range from members of the staff of the Desert 

 Laboratory. 



Bvaporation and Other Climatic Factors in Relation to Distribution of Plants 

 (by Dr. B. E. Livingston) : 

 The records of the evaporation rates by the use of the porous cup-atmom- 

 eter, which were obtained by Dr. Shreve and a number of collaborators 

 during 1908, were reduced and from the corrected data obtained the iso- 

 atmic lines of United States and Canada for the summer season of 1908 were 

 plotted. Such evaporation data promise to supply the missing factor which 

 has rendered attempts to relate plant distribution to climatology so unsatis- 

 factory. The calculation of the evaporation-rainfall ratio for the summer 

 season for several stations is now in progress. 



Atmometry and the Relation of Evaporation to Other Factors (by Dr. B. E. 

 Livingston) : 

 The porous cup-atmometer and the methods for its operation have been 

 improved, new and satisfactory means of calibration have been devised, and 

 a number of secondary influences of climate and exposure upon the cups 

 have been analyzed, so that the instrument is now available for use by any 

 careful observer. Methods have been devised for the ready determination 

 of the influence of wind, relative humidity, and temperature upon evapora- 

 tion. The importance of the atmometer in ecological studies, as indicated by 

 the work of Transeau, Gager, and Yapp, and by various researches at the 

 Desert Laboratory, has led to a fairly successful attempt to analyze the 

 behavior of the instrument under extraordinary conditions. 



The Physics of Transpiration in Plants (by Dr. B. E. Livingston) : 



The quantitative study of the physics of water-loss in desert plants has 

 been continued. The results of 1908, to the effect that the evaporating power 

 of the air and the stomatal movement determine the amount of transpiration 

 in light of a certain intensity only, have been corroborated. It now seems 

 possible to calculate transpiration from the measured intensities of the 



