358 CAENEGIE INSTITUTION OF WASHINGTON. 



tographs are made of representative quadrats. The vegetation is then 

 removed by cutting near the surface of the soil, after which it is collected, 

 thoroughly dried, and the plant production determined on the basis 

 of dry weight. Thus the relative growth of vegetation as a unit, as 

 well as the comparative importance of the dominants in the various 

 associations, is determined. The method is further useful for determin- 

 ing the effects of mowing at different seasons, of grazing, and of other 

 disturbances. The results thus far obtained indicate a rather direct 

 correlation between available water-content and plant production, but 

 it is hoped to continue the studies throughout the climatic cycle in 

 order to secure a total range of correlation. 



Root Development and Absorption, hy J. E. Weaver. 



In connection with the root development of crop plants, a series of 

 experiments on barley was made to determine the degree of absorption 

 at different levels throughout the period of growth. Cylindrical sheet- 

 metal containers, 18 mches in diameter and about 42 inches deep, 

 were placed in trenches in the soil near the crop plots at Lincoln in such 

 a manner that the plants in them grew under fairly normal field condi- 

 tions. These containers were filled with soil and subsoil taken from 

 the trench. The soil from each 6-inch level was kept separate, thor- 

 oughly mixed to insure uniform texture and water-content, and then 

 placed in the containers (16 in number) in such manner that when com- 

 pacted the soil of the containers was very similar to that surrounding 

 them on the outside. A wax seal, consisting of 85 per cent paraffin 

 and 15 per cent petrolatum, was melted and poured upon the soil 

 quite hot in order to separate the soil in a number of containers into 

 layers 6 inches deep, with a known water-content. The efficiency of 

 the seal in preventing water movement was tested by numerous check 

 containers. The ease with which the roots of crop plants penetrated 

 the seal was shown both by their distribution in the soil mass and their 

 normal development when compared with plants grown m unsealed 

 containers and in experimental plots. The first seal was inserted at a 

 depth of 6 inches. The plants were permitted to grow thickly in rows 

 through a slit 1 inch wide and 18 inches long, through the sloping 

 wooden roof of the container. By this method it is possible to remove 

 the containers for root examination and soil-moisture readings from 

 time to time, and to determine the actively absorbing areas of the roots 

 at any period in the development of the plant. The method lends itself 

 readily also to the study of root development in soil layers of different 

 texture, different water-content or air-content, and likewise to experi- 

 ments in soil fertility. 



Climatic Cycles, hy F. E. Clements and A. E. Douglass. 



In further studies of the correlation between climatic cycles and tree- 

 growth, a standard curve has been constructed for Sequoia, reaching 



