132 ROOT DEVELOPMENT IN THE GRASSLAND FORMATION. 



poorly supplied with major branches, rarely more than two occurring on a 

 single plant. These were about 2 mm. in diameter and originated at any 

 depth from 4 inches to 3 feet. Their usual lateral spread, extent, and degree 

 of branching are well shown in figure 36. However, some rather marked 

 differences in the degree of development of major laterals were found. The 

 above description, as usual, is for roots developed near the center of the plats. 

 Those nearer the periphery, where competition was much less keen, were not 

 only larger in both top and root diameters, but there was also a much greater 

 development of large lateral branches, in some cases approaching that of the 

 specimen shown in plate 18, b. This is a somewhat isolated plant one year old 

 and excavated near Central City (see p. 23). Waldron (1911: 409) reports a 

 a similar condition in the development of alfalfa roots in plat experiments. 

 Throughout its course the tap-root and its larger branches are furnished with 

 many small lateral branches, varying in length from a few millimeters to 

 several inches. Only the tan-colored roots originating in the surface 2 feet of 

 soil were at all well rebranched. The younger, glistening white roots of the 

 deeper soils branched not at all or only poorly, except where they occurred in 

 the crevices of the jointed subsoil. Here, perhaps because of better aeration, 

 they rebranched somewhat profusely, the delicate rootlets with glistening 

 white hairs contrasting markedly with the dark-colored soil. Nodules were 

 of frequent occurrence to depths of 3 or 4 feet. 



Several of the sweet clover plants in the upper plats reached maximum 

 depths of 6. 5 feet. The tap-roots had diameters ranging from 4 to 9 mm. The 

 lateral roots were not well developed in the surface soils, but were much better 

 developed in the deeper moist loess subsoil, rather large laterals often arising 

 at a considerable depth. Often the last 8 inches of the root was entirely 

 destitute of branches. Clusters of nodules, 5 to 9 mm. in diameter, were not 

 infrequent in the first 2.5 feet of soil, while below this depth many smaller 

 ones occurred. These data are summarized in table 14. 



Table 14. — Development of sweet clover. 



Brome-grass (Bromus inermis). — On July 10, a preliminary examination 

 of the development of the roots of brome-grass was made. The plants in the 

 lowland plats were 1.2 feet high and in excellent growth. In the upland plats 

 the stand was much poorer and the plants had attained an average height of 

 only 0.5 foot. In the low moist soil the roots were abundant to a working 

 depth of 2.3 feet, a few reaching 3.4 feet; in the upland plats the working depth 

 was practically the same, although many roots penetrated deeper. 



A final examination was made on August 20, when the grass was nearly 4 

 months old. At this time the lowland plants averaged 1.3 feet in height, 

 although some had put forth flowering stalks, which, of course, were much 

 taller. Only about half a stand was present in the upland area, no flowering 

 stalks had yet developed, and the plants were only 6 inches in average height. 

 This grass spreads by rhizomes and forms a dense sod. The roots form a close 

 growth, filling the soil to a depth of about 2 feet. The dark-brown roots, 



