ROOT SYSTEMS OF MIXED-PRAIRIE SPECIES. 



51 



in texture. The tap-roots keep their dominance throughout and at a depth of 

 5 feet one was still 2 mm. in diameter. They reached a maximum depth of 

 5.3 feet. No branches were given off in the first 6 to 8 inches of soil, but below 

 this-point branches from 2 to 6 mm. in diameter arose. These seldom ran out 



Fig. 20. — Meriolix serrulata. ' 



laterally for greater distances than a foot from the tap. They branched 

 only poorly. The fleshy, dark-tan-colored root is kinked and curved and the 

 smaller branches especially are very brittle. Even the root-tips end abruptly 

 with only a few branches. Figure 21 illustrates the dominance of the tap-root, 

 paucity of small laterals, and the depth of penetration. 



Eriogonum annuum. — This tall, erect annual is a very common component 

 of sandhills vegetation, frequently occurring in considerable abundance. The 

 plants examined near Haigler, Nebraska, were 2 feet tall and just ready to 

 blossom. It has a tap-root 3 to 5 mm. in diameter, yellowish in color, and 



