88 ROOT DEVELOPMENT IN THE GRASSLAND FORMATION. 



from that of plants of the sandhills. Under the latter conditions the root system 

 is much shallower and much more abundantly supplied with surface laterals. 

 These are fairly well rebranched and the tap-root and main laterals, which branch 

 and rebranch profusely, have a strong tendency to run obliquely or even hori- 

 zontally rather than vertically as in the plains ecads (Weaver, 1919:118). 



Carex pennsylvanica. — Because of its early growth and flowering habit, 

 this sedge forms conspicuous societies in the prevernal aspect. It has a wide 

 distribution throughout the grassland formation and where abundant (like 

 C. filifolia and C. stenophylla) it affords considerable early forage before many 

 of the grasses resume growth. 



Several plants were excavated on a well-covered sandhill near Central City. 

 The characteristic small plant tufts were connected by means of rhizomes. 

 These are rather coarse, about 2 mm. in diameter and 1 to 10 inches in length. 

 Some of the very abundant fibrous roots spread laterally in the sand at a 

 depth of only 2 or 3 inches to distances of a foot or more before turning down- 

 ward (plate 17, a.) The roots originate from the rhizomes as well as from the 

 base of the clumps, and completely fill the soil to a depth of 2 feet. Many 

 of the larger roots pursue an almost vertically downward course, reaching a 

 maximum depth of 2.5 feet. All are well supplied with laterals, which, al- 

 though usually not over an inch in length, are rebranched to the third and 

 fourth order. These are exceedingly abundant in the upper portion of the root 

 system, where they form tangled mats, but also extend to the well-branched 

 tips, thus giving this sedge a wonderfully efficient absorbing system. The 

 rhizomes and older roots are dark brown in color, while the younger ones are a 

 light tan. 



At Seneca a few roots of this species penetrated vertically downward to a 

 depth of 2.9 feet, but the working depth was 2 feet. The lateral spread and 

 profuse branching were identical with that just described. 



At Colorado Springs, where this species was examined in the hard loam, 

 the lateral spread was only 2 or 3 inches from the base of the tufts. The 

 working depth was about 1.7 feet, although some roots penetrated to a depth 

 of 3 feet. Branching was very similar to that found in the sandhills, but 

 scarcely so profuse. 



Redfieldia flexuosa. — This stout, perennial grass often reaches a height of 

 2 or 3 feet. It is the most abundant and important of blowout pioneers, and, 

 while found mixed with other species, it is very frequently the only plant 

 present in such situations (plate 9, c). While it is of very little grazing value, 

 it is of great economic importance as a sand-binder. It has been excavated in 

 the sandy region of central Colorado, about 40 miles southeast of Colorado 

 Springs, together with Calamovilfa longifolia, Andropogon hallii, Artemisia 

 filifolia, and numerous other species. Here it was found to have a widely 

 spreading surface root system in addition to deeper-seated roots, some of which 

 extended in the dry sand to a depth of about 5 feet. 



At Central City they were again examined and, as pointed out heretofore, 

 in a much more humid climate. Moreover, the sand of these dunes, being of 

 local extent, is often slightly intermixed with darker soil. Several clumps of 

 plants were excavated in the more open places on the slope of a large dune, 

 otherwise well-covered with Andropogon hallii, Calamovilfa longifolia, and 

 Sporobolus cryptandrus (plate 10, b). The tough, wiry, much-branched 

 rhizomes are often many feet long. They may sometimes be traced for 

 distances of 20 to 40 feet on the surface where the sand has been blown away. 

 They extend in all directions, from parallel with the soil surface to vertically 

 downward, and with the multitudes of tough, wiry roots originating from them 



