248 JOHN ERNST WEAVER 



Astragalus (Phaca) arrectus (Fig. 9) 



Although a common prairie species, this plant is less abundant 

 than Lupinus ornatus. Like most of its neighbors on the dry 

 hillsides, it flowers early and dries up during the first week of 

 July. 



Six plants were examined on a southwest slope with an average 

 root depth of 4 feet and 7.8 inches. The strongly developed tap 

 root is seldom over 0.5 inch in diameter, usually pursues a course 

 directly downward, and sends out many strong laterals at vari- 

 ous depths. These laterals sometimes branch off even at 3 

 inches below the soil surface, and, like other laterals which may 

 be thrown off all the way to the tip, often run in a rather hori- 

 zontal direction before again turning downward. Like all the 

 laterals, the tap root is usually profusely branched and the tip 

 is also well provided with branchlets. One case was observed 

 where the end of the tap root entered a worm hole at a depth of 

 47 inches and extended downward in the hole for 9 inches to its 

 end, without branching, but it was densely covered with root 

 hairs. Astragalus roots have a light tan color. The shortest 

 root-system reached a depth of 3 feet and 4 inches; the longest, 

 5 feet and 10 inches. 



(To be continued.) 



