90 ROOT DEVELOPMENT IN THE GRASSLAND FORMATION. 



At Central City, a station of higher rainfall, the root penetration was much 

 greater. Here it was excavated on a grassy hillside, where the elaborate 

 system of rhizomes, lying at a depth of 1 to 6 inches, quite effectively held the 

 sand from blowing. Of the large number of roots originating from these 

 rhizomes, some spread obliquely at various angles below 15 degrees from the 

 ground-line, reaching horizontal distances from the point of origin of 1 to 3 

 feet. Others penetrate rather vertically downward, ending mostly in the 

 third foot of soil or somewhat deeper, a few reaching a maximim depth of 3.9 

 feet. The diameter of these rather coarse roots varies from 1 to over 2 mm. 

 Throughout their entire course all were copiously branched with mostly short 

 branches ranging from 0.5 to 3 inches in length. Not infrequently 6 to 9 of 

 these bunches occurred on a single linear inch of root. Longer rootlets were 

 rather rare, but these small branches were abundantly supplied with rootlets 

 4 to 8 inches long. 



At Haigler, Nebraska, further examination was made in an old road where 

 Calamovilfa was also excavated. The great depth of penetration was quite 

 surprising. Numerous roots were traced to a depth of about 8 feet, while 

 some penetrated 3 inches deeper. Many branches spread laterally in a more 

 or less horizontal manner for distances of 3 to 12 inches. The soil was moist to 

 a depth of at least 10 feet, extra moisture being afforded by run-off into the 

 depression made by the roadway. 



At Yuma, Colorado, a maximum depth of 7.3 feet was determined for this 

 species (fig. 31). Here it was growing in a well-covered dune area. The 

 surface roots, especially in the first 2 feet of soil, were exceedingly well clothed 

 with fine laterals, as many as 30 to 50 occurring along a linear inch of one of 

 the fibrous roots. Below this depth some of the branches were longer, often 

 extending in a somewhat horizontal direction for distances of 4 to 8 inches or 

 more. These, like the main roots, are well clothed with smaller rootlets. 

 The final 6 to 12 inches of the growing roots are somewhat enlarged in diameter 

 (2 to 3 mm.) and are destitute of branches. While many roots ended in the 

 third and fourth feet, the soil was well filled to a depth of 6.5 feet. Indeed, 

 even below 6 feet the soil is penetrated by a mat of roots whose profusely 

 branched laterals rather completely occupy it. 



Summarizing the data on the three sandhill grasses, Redfieldia 

 flexuosa, Calamovilfa longifolia, and Andropogon hallii, we find that all 

 three penetrate more deeply at all of the other stations than where first 

 examined in the dune area southeast of Colorado Springs. At Central 

 City, under a precipitation 75 per cent greater than in the former area, 

 the root depth in every case was 1.5 feet or more deeper. But on the 

 steep hillside at Seneca and in the sand at Yuma, as well as in the 

 abandoned road at Haigler, the root depth of the sand-reed and the 

 bluestem both exceeded that at Central City. At Haigler, the great 

 penetration, which in fact was the deepest recorded, may be due to the 

 excess of moisture collecting in the abandoned road. In the light of 

 these further studies it seems not improbable that the roots of the plants 

 near Colorado Springs were not fully developed. The life history of 

 each of these species should be studied. Waterman (1919), after a 

 study of seedling development on the sand dunes near Chicago, 

 suggests that after " giving due weight to the possibility of moisture, 

 oxygen-content, and penetrability of the sand as influencing factors, 



