ROOT SYSTEMS OF MIXED-PRAIRIE SPECIES.. 71 



depth of 0.3 foot, it gave off 8 major branches, 4 to 5 mm. in diameter; there 

 were also 5 smaller ones. Below the first foot the branching was very sparse 

 to the end of the tap-root. One of the largest laterals, which originated at a 

 depth of 0.8 foot, spread horizontally from the base of the crown to a distance 

 of nearly 3 feet, where at a depth of only 2 feet it gave off 5 major branches, 

 each about 2 mm. thick. These spread widely and ran for distances of 1 to 2 

 feet before turning downward. Besides these branches, the root was furnished 

 with numerous unbranched laterals less than an inch in length. The root-tips 

 were only poorly branched in the very hard soil. Nodules about a millimeter 

 in thickness and 2 mm. long occurred at intervals throughout its entire length. 

 The other specimen reached a maximum depth of 4.3 feet, although it seems 

 certain that in less compact soil the root depth would have been much 

 greater. In the first 1.2 feet of soil it gave off 20 branches, 2 mm. or more in 

 diameter, 3 of the larger ones being 4 mm. in width. There were also great 

 numbers of smaller ones, so that the soil was quite filled with roots to a depth 

 of about 3 feet. Below 1.5 feet on the tap-root branching was much less 

 profuse and the laterals were smaller in size. The lateral spread was again 

 very pronounced and some of the larger, widely spreading roots reached depths 

 of nearly 4 feet. None of the root-tips were well-branched. Clusters of 

 tubercles were found at various depths, forming x, Y, and H patterns 5 to 

 6 mm. in diameter. Summarizing, we find this legume has a tap-root which 

 penetrates rather deeply and is abundantly supplied with numerous, rather 

 coarse, moderately branched but widely spreading laterals, most of which 

 originate in the surface 0.3 to 1.5 feet of soil. 



This completes the list of plants whose root systems have been 

 examined for the first time in mixed prairie. It will be best, however, 

 instead of summarizing root habits here, to postpone this to the end of 

 the chapter on ecads, as we may thus include a large number of species 

 which have been examined in other habitats, but for the first time under 

 growth conditions of the mixed prairie. To this list we may also add 

 certain dominant and subdominant species which heretofore have been 

 described only in mixed prairie (Weaver, 1919), but which have now 

 been examined in a wide range of habitats. 



