ECADS. 79 



usually more than 1 or 2 mm. in diameter. They soon become more or less 

 threadlike, with small rebranched rootlets from a few millimeters to several 

 inches in length. Many of the larger roots reached a depth of 5 feet, while the 

 tap-root ended in the moist sand at a depth of 8.4 feet. The root habit was 

 very similar to that found in the hard loam soil of the plains, except for the 

 more profuse branching and greater depth of penetration. However, this 

 was a much larger specimen than any found in the mixed-prairie habitat. 



Lygodesmia juncea. — This composite is of frequent occurrence, often be- 

 coming ruderal, especially in drier situations throughout the prairie-plains 

 grassland. It is especially interesting because of its xeroid-shoot habit. It 

 has been examined both in the subclimax prairie near Peru, Nebraska, and in 

 the mixed prairie at Colorado Springs. In the mellow loess soil at the former 

 station the tap-roots were found to penetrate vertically downward to depths 

 of 15 or 20 feet or more. The brittle, fleshy roots are usually 2 to 6 mm. in 

 diameter and do not branch at all, except for tiny laterals less than a milli- 

 meter in thickness and an inch in length, which come off very sparingly at 

 intervals of 6 to 12 inches. In the hard loam soil at the mixed-prairie station 

 the depth of penetration of the two plants excavated was only about 6 feet. 

 The root diameter was about 7 mm. Throughout its course the root was 

 very much curved and twisted, nor did it penetrate directly downward. 

 Several large, crooked, wide-spreading branches were given off, but practically 

 no small ones. 



This species was encountered quite frequently, not only among the native 

 vegetation but also in excavating crop plants, among which it is often quite an 

 abundant weed. The root habit varied somewhat between the two extremes 

 above noted. In the sandy-loam soils the roots were less crooked and kinked 

 and had fewer or no major branches, while in the harder soils, or layers of 

 harder soil, these characters were more pronounced. Roots were found to 

 penetrate well beyond a depth of 8 feet in two or three of the trenches dug at 

 Burlington, Colorado, and also in the silt-loam at Colby, Kansas. Unques- 

 tionably this xerophyte is a deep feeder. 



Andropogon scoparius. — Little bluestem ranks as one of the most important 

 grasses of subclimax, true and mixed prairie. Its wide range can be largely 

 explained by a consideration of its excellent and plastic root system, its 

 methods of propagation, and its sod and bunch-forming habits. It is an 

 economic species of much importance and warrants careful study. 



This grass has been examined in two types of soil in the true prairies near 

 Lincoln. In clay-loam soil with a clay subsoil several plants had a root depth 

 of about 5.5 feet, while in a porous gravelly soil mixed with sand and underlaid 

 with a rocky subsoil of decayed sandstone at a depth of 3 feet, none of the roots 

 reached depths greater than 2.3 feet. Branching and lateral spread were 

 much the same in both cases, but emphasized somewhat in the poorer soil 

 type (Weaver, 1919:5). 



At Colorado Springs the surface portion of the root system was well 

 developed, especially well-branched laterals spreading to 1 to 1.2 feet on all 

 sides of the bunches in the surface 0.3-foot soil layer. Below and inside of 

 these, at all angles to the vertical, the roots were very abundant. Most of 

 them penetrated to about 3.5 feet, and the maximum depth of several roots 



was 6 feet. 

 During 1919 this species was excavated in the silt-loam soil of the mixed prairies 



near Phillipsburg. The roots were still very abundant at 4.5 feet and not a few 

 reached a maximum depth of 5.2 feet. The roots occur in very large numbers, 

 but are only 0.1 to about 0.8 mm. in diameter. Some spread laterally nearly 



