ROOT SYSTEMS OF MIXED-PRAIRIE SPECIES. 61 



threadlike sublaterals 1 to 3 inches in length, and sometimes so numerous 

 as to form brushlike mats. Many of the laterals extend out almost parallel 

 with the surface or onty slightly obliquely, the larger ones to distances of 1 

 to 2.5 feet before turning rather abruptly downward. They may descend 

 vertically, but frequently pursue a more or less tortuous course, some to a 

 depth of over 6 feet. Below the first foot of soil the branches of the tap-root 

 are usually much shorter. However, the tap-root is often well-branched 

 throughout. These tap-roots, winch keep their identity to the end, were 

 traced to a depth of 8 feet. The specimens examined were all from 1 to 1.5 

 feet in height and each had from 5 to 10 large branches. The great extent of 

 this large root system may be made more apparent by a study of figure 23. 



Anogra cinerea. — This evening-primrose is widely distributed throughout 

 the drier parts of the grassland formation. It is often an important sub- 

 dominant in the mixed-prairie vegetation of sandhills. A family of several 

 plants was examined on a poorly stabilized sandhill. Many of the plants 

 were connected by means of rhizomes which ran at a depth of only 4 to 6 

 inches below the surface. Some of these rhizomes, although 2 mm. in diameter 

 and over 2 feet in length, were without shoots and had practically no roots. 

 The tap-roots on some of the larger specimens were 14 to 16 mm. in diameter. 

 They were traced to a depth of over 9 feet, at which point some were still 

 2 mm. thick. Further excavation was not made because of the caving sandy 

 trench-walls. A glance at figure 24 shows that this plant has a deeply placed 

 root system, and probably does little absorbing in the surface soil. The strong 

 laterals, some of which, at their point of origin, are of almost equal diameter 

 with the tap-root, spread very widely and penetrate to depths of from 7 

 to 9 feet. Compared with many species, they are rather poorly branched, 

 but near the root-ends of the larger laterals, as well as sometimes on smaller 

 ones, large clusters of much-branched rootlets occur. These rootlets are from 

 0.5 to several inches in length and fairly well rebranched. The roots are 

 yellowish in color, rather fleshy, and provided with a tough stele. Like the 

 preceding species, this coarse, rather meagerly branched root system is very 

 deep-seated, but unlike the sage it is poorly equipped for absorption in the 

 surface soil. 



Chrysopsis hispida. — This rather low, spreading composite, like C. villosa, 

 has a wide range throughout the grassland formation. In the sandhills and 

 other more arid regions it is a society-forming subdominant. Several plants 

 were excavated on a sand dune near Yuma. The soil was quite moist to a 

 depth of over 9 feet. The root habit of this species is similar to that of 

 Chrysopsis villosa, especially when grown under similar edaphic conditions 

 (Weaver, 1919:117). The grouping of the plants is accounted for by the 

 root offshoots, as shown in figure 25. The tap-root of the largest plant 

 examined was 16 mm. in diameter and it was traced to a depth of 9 feet, when 

 the danger of caving of the trench became so great that work on it was aban- 

 doned. For the first 2 or 3 feet of its length the tap is woody; it descends 

 rather vertically downward and usually keeps its identity throughout. The 

 branching in the first 2 feet of soil is especially well developed. Several large 

 laterals and almost countless smaller ones run off at right angles from the tap 

 to distances of 1 to 2.5 feet, where the smaller ones may end. The larger ones, 

 which are 2 or 3 mm. in diameter, may have an even greater lateral spread 

 before they turn downward. The branching throughout is irregular and even 

 in the deeper soils the roots may meander still farther away from the base of 

 the plant. While the smaller laterals are exceedingly abundant, they are 



