82 ROOT DEVELOPMENT IN THE GRASSLAND FORMATION. 



Andropogon furcatus. — Like the preceding, this bluestem is also dominant 

 among prairie grasses. Its smaller resistance to drought, which is shown both 

 by its local and general distribution, can easily be understood when this 

 taller and deeper but coarser-rooted species is compared with the shorter, 

 finer-rooted and more profusely branched A. scoparius. While big bluestem 

 occurs upon high prairies, it makes its best development in the draws and on 

 lower land (plate 6, b, and figs. 11 and 13). It is an important mixed-prairie 

 species, but does not extend into such dry areas as does A. scoparius. The 

 root depth of the big bluestem has already been contrasted where the plants 

 were growing on the high and low prairie at Lincoln (p. 41). 



Further examination of this species was made at Phillipsburg, Kansas, 

 where it occurs as a dominant among the tall-grasses (p. 75). The very 

 abundant, rather coarse roots grow both vertically and obliquely downward, 

 thoroughly occupying the soil and forming a dense sod. Some of the roots 

 extend laterally in the surface 0.5 foot of soil to a distance of 0.7 to 1.2 feet 

 before turning downward. The working depth is nearly 7 feet. The roots all 

 branch profusely, the main laterals being mostly 0.2 to 0.5 foot in length. The 

 ends of the roots are extremely well branched. Little difference was found in 

 the root habit of these plants of the mixed prairies and those in the true prairie 

 at Lincoln, except in greater depth of penetration. At Phillipsburg some of 

 the deeper roots reached a level of 8.7 feet, while at Lincoln 6.8 feet was the 

 greatest depth recorded for high-prairie species, those in the low prairie having 

 a root system of even lesser extent (p. 41). However, in the mellow loess soil 

 of the subclimax prairie at Peru, Nebraska, root depths of over 9 feet were 

 recorded. A 4-months-old specimen, grown in alluvial soil on a lowland area 

 near Lincoln, is shown in plate 18, a. 



Artemisia filifolia— The sand-sage is often a very important species in the 

 structure of mixed-prairie vegetation in sandy areas. This is due both to its 

 shrubby habit and its great abundance. It is indicative of a light type of soil 

 with considerable moisture penetration. It rarely occurs on the more com- 

 pact silt-loam soils. 



Two large specimens were examined on a fairly well-covered area on a sand- 

 hill. The root system is dominated by a strong tap-root (plate 19, a), from 

 which arise great numbers of long, profusely branched laterals. One tap-root 

 was traced to a depth of over 8 feet. The strong, vertically descending, 

 woody tap-root tapers gradually and uniformly. Some of the larger branches 

 had a lateral spread of 4 or 5 feet and reached depths of 4 to over 6 feet. Most 

 of the branches, both large and small, originated in the surface 3 feet of soil, 

 and with their profuse laterals formed an extensive absorbing system in the 

 surface 3 or 4 feet of sand. Little difference was found between these plants 

 and those of the same species excavated near Colorado Springs (Weaver, 

 1919:73). 



Muhlenbergia pungens. — This grass is a regular component of blowout 

 communities and is not infrequently dominant. It is characterized by tufted 

 stems which arise from rootstocks and form cushions or mats that lie close to 

 the sand (plate 9, c) and by scabrous, narrow, rigid leaves. 



This important sandhill grass was examined about 40 miles southeast of 

 Colorado Springs, on the rim and grassy top of a blowout, where it was growing 

 very abundantly. It was found to have a rather shallow but widely spreading 

 root system, none of the roots penetrating the dry sand to a greater depth than 

 2 8 feet. 



' Careful examination of this species was made at Central City, Nebraska, in 

 the extra-regional sand dunes. Here it was growing in the usual mats in pure 



