ECOLOGY. 333 



of phytometers. The question of the rate of translocation and its rela- 

 tion to the total carbohydrate present at a particular time has been 

 approached from several angles. Chief among these are the determina- 

 tion of the amount and rate of diffusion into shaded areas of the leaf, 

 and of the relative amount at different times of the day in paired 

 leaves, one of which has had the bundles of the petiole severed to pre- 

 vent translocation to the stem. Studies have also been made of the 

 comparative efficiency of the leaves of closely related varieties of crop 

 plants, and the results confirm the view that this method will prove of 

 great value in the selection of individuals as well as of varieties for 

 development. 



Behavior of Stomata, by G. V. Loftfield. 



The investigation of the behavior and efficiency of stomata in a large 

 number of cultivated and native plants has been continued during the 

 summer and autumn, chiefly at the Experiment Station of the Ameri- 

 can Smelting and Refining Company at Salt Lake City, through the 

 courtesy of the director, Dr. P. J. O'Gara. The major attention has 

 again been centered on the relation of stomatal opening and closing to 

 the efficient factors, and especially to wilting and recovery. Special 

 methods have been devised to show the effect of light and humidity 

 and to check out the errors involved in the use of cut stems. Repeated 

 studies have been made to measure the regulatory action of stomata 

 in transpiration, and particularly in the case of plants wilting naturally 

 and artificiallj^ Special consideration has been given to the amount 

 of decreased transpiration in periodic daily wilting, as well as in plants 

 which fail to recover. Opportunity has also been found to study the 

 absorption of carbon dioxid as determined by the amount of photo- 

 synthate made and to ascertain the effect of stomatal movement upon 

 the absorption of sulphurous acid. The results of further studies con- 

 form with those already obtained in indicating that most if not all 

 herbaceous species possess stomata with a decisive regulatory action 

 at the time of wilting, even though they show little activity under less 

 severe conditions. 



The Ecology of Root Systems, by J. E. Weaver. 



The preliminary results of the ecological study of the root systems 

 of grassland species have appeared during the year under the title 

 "The Ecological Relations of Roots." During the present field season 

 the investigation of the root systems of dominants and subdominants 

 of prairies, mixed prairies, and short-grass plains has been greatly 

 extended. The trench or pit method heretofore described has been 

 employed. The examination of roots with reference to their relation 

 to the nature of the soil, the amount and penetration of the water- 

 content, and their competition with each other has been made at 16 sta- 

 tions in the States of Kansas, Colorado, South Dakota, and Nebraska. 



