PRAIRIE PLANTS OF SOUTHEASTERN WASHINGTON 



243 



SCOPE AND METHODS OF THE STUDY OF ROOT-SYSTEMS 



The object of this study was to determine the depth at which 

 the most important prairie plants obtain their water supply; 

 to get accurate data on the distribution and extent of the root- 

 systems in the soil ; and to examine enough plants of each species 

 so that the conclusions might be thoroughly reliable. Finally, 

 it was hoped to use these data in helping to solve the problems 

 of succession and structure of prairie vegetation. 



Owing to the tenacious structure of the soil and the great 

 depth of most roots, it was found impracticable to wash out the 



1 





Fig. 6. Lumps of soil taken at a depth of 5 feet on a northwest slope, showing 

 the numerous large earth worm burrows. They are from 7 to 8 mm. in diame tor 

 and reach depths of more than 13 feet. 



root-systems. The method finally employed was to dig a trench 

 2 feet wide and 8 to 16 feet long to a depth of about 6 feet on the 

 hillside where roots were to be examined. This offered an open 

 face into which one might dig with a hand pick, and, after suffi- 

 cient practice, and acquaintance with the soil texture, success- 

 fully excavate a root-system almost in its entirety. Of course 

 the trenches were deepened as work progressed and the working 

 level sometimes reached to a depth of 10 or 12 feet. (See fig. 5.) 

 Five of these larger pits were used and several smaller ones. 



THE PLANT WORLD, VOL. 18, NO. 9, '915 



