14 



Development and Activities of Roots of Crop Plants. 



The root systems of the wheat plants examined agreed with the statement 

 of Rotmistrov, for not only at this period did these primary roots penetrate 

 deepest, but they lived and continued to grow and function until the plant 

 matured, at which time they had reached greater depths than any of the roots 

 that formed later (fig. 3 c). Of these primary roots a few grew almost ver- 

 tically downward, but by far the greater number passed off obliquely to a 

 distance of 0.5 to 1.3 feet and then, turning downward, pursued a zigzag but 

 generally vertical course to a depth of 3.9 to 4.2 feet. The maximum depth 



Fiq. 3.— A. Marquis wheat 20 days old; B. 70 days old. C. Durum wheat 60 days old. 



of penetration was 4.5 feet. These main roots were yellowish in color and 

 quite tough. Throughout their course, excepting the last 8 to 12 inches, 

 they were quite abundantly branched, the branches varying from a few milli- 

 meters to 2 or more inches in length. These branches were themselves often 

 rebranched. Just below the surface of the soil another set of roots arose 

 from a node on the main stalk. These passed out almost horizontally in 

 all directions to a distance of 6 to 8 inches. Some of these, however, were 



