70 ROOT DEVELOPMENT IN THE GRASSLAND FORMATION. 



were about 2.1 feet high, fully mature, and in seed. The clumps each had 25 

 flowering stalks. From the base of the clumps 80 to 150 fibrous roots originated. 

 These roots were about a millimeter or less in diameter. The lateral spread 

 on either side of the clump was only 0.7 to 1 foot. Most of the roots de- 

 scended rather vertically or at such angles that at no depth were they more 

 than 1 to 1.2 feet horizontally away from the base of the plant. The working 

 depth was found to be 2.3 feet and no roots were found at a depth greater than 

 3.2 feet. They are well supplied with laterals, seldom over 2 inches in length, 

 but fairly well rebranched with short sublaterals, so that the absorbing system 

 as a whole, although limited to the first 2 or 3 feet of soil, is a very good one. 



Carex filifolia. — This species, with Carex stenopliTjlla, sometimes plays a 

 role of almost equal importance with the grasses in plains and mixed-prairie 

 vegetation. They are important range species, since they afford considerable 

 forage early in the spring before many of the grasses have resumed growth. 

 The tough, black, wiry roots of these species bind the surface soil so firmly that 

 new roads through the grassland are very rough for several years until the root 

 clumps are worn through. 



Several plants of Carex filifolia were examined in the mixed prairies near 

 Ardmore. The plants often grow in clumps 4 to 6 inches in diameter. Not 

 infrequently they die out in the center and grow only around the periphery of 

 the clumps. They are furnished with an enormous number of tough, wiry 

 roots, a millimeter or less in diameter. These seldom descend vertically, but 

 run obliquely away from as well as under the plant, forming a great tangled 

 mat to a depth of 1.2 to 1.5 feet. Laterals were traced horizontally away from 

 the plant to a distance of 2.7 feet and at a depth of only 0.3 to 0.5 foot. While 

 the larger and older roots are not so well branched for the first few inches from 

 their origin, a very large number of smaller, profusely branched roots care for 

 surface absorption close to the clump. All of the roots are supplied very 

 abundantly with laterals ranging in length from 0.5 inch to over 3 inches. 

 These terminate in brush-like masses of laterals, the ultimate branches being 

 very fine and delicate. Not only is the surface soil filled with roots, but many 

 go obliquely downward, criss-crossing at various angles, and reaching a working 

 depth of about 4 feet. Not a few were found below this level, while some 

 reached a maximum depth of 5 feet 2 inches. The roots end in brush- 

 like branches. The younger roots, like those of Carex pennsylvanica, vary 

 from light-brown to nearly black in color, while the older exposed and dead 

 ones are black. This, with their wiry, matted appearance, accounts for the 

 vernacular name "nigger wool" which is applied to this plant. The abundant, 

 deep, widely spreading roots of these plants were excavated in the same soil 

 type as that described for the preceding species. 



Astragalus drummondii. — This legume was also examined in the mixed 

 prairies at Ardmore, where it forms extensive societies, as in many places 

 throughout the more arid portions of the grassland formation. In digging the 

 trench, the first 4 feet of soil was found to be hard Pierre clay. This was 

 underlaid by a 1.5-foot stratum of sand and coarse gravel, so closely compacted 

 that it was necessary to remove it with a pick. Below 5.5 feet this gave way 

 to a stiff sandy loam. Two large specimens were examined. Each had a 

 strong, woody tap-root 17 mm. in diameter. The crown of each plant was 

 about 1.5 inches below the soil surface. The tap-roots descended rather 

 vertically downward and tapered rather rapidly. In the one plant at a depth 

 of 1.7 feet it was only 3 mm. in diameter, while in the other it was about a 

 millimeter in diameter at a depth of 2.7 feet. The first plant examined 

 reached a maximum depth of 4 feet. In the first foot of soil, beginning at a 



