LIST OF ILLUSTRATIONS. 



PLATES. 

 Plate 1. 



A. Iowa Silver Mine corn 57 days old; root system shown in fig. 8. 



B. Potato 2.3 feet high on July 8; root system shown in fig. 11. 



C. Corn on September 2; root system shown in fig. 9. 



D. Trench used in examining the roots of cereals. 

 Plate 2. 



A. Marquis Spring wheat at Burlington, 1920. 



B. Marquis Spring wheat from a square meter at BurUngton (left), Phillipsburg, and 



Lincoln. 

 Plate 3. 



A. White Kherson oats from a square meter at Burlington (left), Philhpsburg, and 



Lincoln. 



B. Manchuria barley from a square meter at Burlington (left), Philhpsburg, and 



Lincoln. 

 Plate 4. 



A. Four hundred plants of alfalfa from lower crop plats (left) and upper crop plats 



at Lincohi; and from Phillipsburg and Burlington, respectively. 



B. Three hundred plants of sweet clover from lower crop plats (left) and upper crop 



plats at Lincohi; and from Philhpsburg and Burlmgton, respectively. 

 Plate 5. 



A. Wheat from Lincoln (left), Philhpsburg, and Burlington, May 18-21. 



B. Barley from Lincoln (left), Phillipsburg, and Burhngton, May 18-21. 

 Plate 6. 



A. Oats at Lincoln, May 18. 



B. Oats at Phillipsburg, May 19. 



C. Oats at Burlington, May 20. 

 Plate 7. 



A. Wheat from Lincoln (left), Phillipsburg, and Burlington, June 10. 



B. Barley from Lincoln (left), Phillipsburg, and Burlington, June 10. 

 Plate 8. 



A. Oats at Lincoln, June 10. 



B. Oats at Phillipsburg, June 10. 



C. Oats at Burlington, June 10. 

 Plate 9. 



A. Barley grown in container with wax seals at 6-inch intervals. 



B. Same with upper portion of container removed. 



C. Wax seal at depth of 2 feet (left) sho\\dng the penetration of the seal by roots and 



their abundance under field conditions. Fertihzed soil at 2.5 feet depth 

 filled with copiously branched roots. 



D. Arrangement of containers in greenhouse experiment, 1920-21. 

 Plate 10. . . ' . 



A. Development of barley on December 11 in unaerated, fertihzed soil. 



B. Development of barley on December 11 in aerated, unfertilized soil. 

 Plate 11. 



A. Development of crop on March 12 in fertihzed soil. 



B. In unfertUized soil. 

 Plate 12. 



A. General view of one row of containers. May 17. 



B. Detailed view of barley and potatoes. May 17. 

 Plate 13. 



A. Potatoes and barley on June 13. ^ 



B. Native grasses on August 15, at the time of examination. 

 Plate 14. 



A. Development of corn, June 5. 



B. Development of corn, July 10. 



