THE PRAIRIES. 



5 



Ten Eyck (1904:216) examined the roots of A. furcatus at Manhattan, 

 Kansas, and found that they "form a dense, tough sod, from 6 to 8 inches 

 thick, and the subsoil is filled with a great mass of roots." "The roots were 

 broken off at 4.5 feet from the surface, but from their size they must have 

 extended at least 2 feet deeper into the compact clay subsoil." 



Twelve plants were examined near Lincoln. The very abundant roots 

 grow both vertically and obliquely downward, a few almost horizontally, and 

 at once thoroughly occupy the soil and form a dense sod. The roots may 

 extend obliquely away from the bunches to more than a foot before turning 

 downward. The larger roots vary from 0.5 to 3 mm. in diameter and may 

 reach a depth of 6 feet and 10 inches. Most of the plants examined reached 

 depths of over 6 feet (plate 3, a). In locations where a hard clay subsoil 

 occurred the roots were 2 to 2.5 feet shorter. All of the roots branch profusely, 

 the main laterals being from 2 to 6 inches long. However, here again the 

 amount of branching and the length of the laterals are closely correlated with 

 the soil texture, always being less in hard soils. The roots taper so gradually 

 that at 4 feet thay are nearly as large as at the surface. The soil is thoroughly 

 occupied to a depth of 5 feet. The ends of the roots are extremely well 

 branched to the very tip. In color the roots are reddish-brown. They have 

 a very loose papery cortex which is easily removed and reveals the tough, 

 yellowish stele. 



Andropogon scoparius. — This grass is figured by Shantz (1911:56) as 

 extending to a depth of about 5 feet and thoroughly occupying the sandy soil 

 in the bunchgrass association of eastern Colorado. It is interesting to note 

 that the deep-rooted Panicum virgatum also occurs here. 



In these studies plants of this species were examined in two soil tjrpes. The 

 first group was in porous, gravelly soil mixed with sand and underlaid with a 

 rocky subsoil of decayed sandstone at a depth of 3 feet. The other group 

 grew in clay-loam soil with a clay subsoil. In the former habitat none of the 

 roots of the several plants examined reached depths greater than 28 inches, 

 while in the clay loam several plants had a maximum root depth of about 65 

 inches (plate 3, b). The roots are much finer than those of A. furcatus, being 

 only 0.1 to 0.8 mm. in diameter. The lateral spread of the roots is very 

 similar but somewhat more pronounced. Roots are so abundant as to form 

 a dense sod, completely filling the soil to a depth of from 12 inches in gravelly 

 soil and to as much as 30 inches in clay loam. The surface is especially well 

 occupied with dense masses of finely branched rootlets. All the roots branch 

 profusely to the third or fourth order, many of the branches being over 30 

 inches long. The deeper soil (from 30 to 60 inches) is fairly well occupied. 

 The roots are light-brown in color and have a very thick cortex which peels 

 off easily, thus exposing the tough yellowish stele. The deeper roots are 

 lighter in color, profusely branched, and very brittle. 



Andropogon nutans. — Goldstem is a dominant in the subclimax prairie. 

 Like the other andropogons and Panicum virgatum, it also matures late in 

 summer. It is one of the deeper-rooted prairie grasses. Of the 5 plants 

 examined the maximum depth of root varied between 51 and 59 inches 

 (plate 3, c). These were growing in a clay-loam soil which extended to a 

 depth of 3.5 feet and below which occurred pure sand. The roots vary from 

 2 mm. to less than 0.5 mm. in diameter. They are very abundant, spread 

 laterally but little, and completely occupy the soil, branching profusely to the 

 second and third order. Within a foot from the surface, however, most of 

 the roots become less than 0.5 mm. in diameter, forming a dense network to 

 a depth of about 3 feet. Even in the fourth foot the roots are quite numerous. 



