66 ROOT DEVELOPMENT IN THE GRASSLAND FORMATION. 



sisted of a dark-colored sandy loam. The clumps are connected by strong 

 rhizomes 2 or 3 mm. in diameter and of a variable length, but they usually 

 give rise to new clumps at intervals of 3 to 5 inches. Numerous roots arise 

 from the base of the clumps as well as from the rhizomes. These roots are 

 1 to 1.5 mm. in diameter. They vary in number from 3 to more than 16 from 

 an individual clump, depending upon its size. Many of these run off in a 

 direction almost parallel with the soil surface or only slightly obliquely, to a 

 distance of 1 to 1.5 feet, or sometimes even further from the base of the clump 

 before turning downward (plate 15, b). They are abundantly supplied with 

 laterals, which are usually only 1 to 1.5 inches in length, but exceedingly well- 

 branched with delicate sublaterals. This dense network of roots completely 

 occupies the soil to the working depth of 1.7 feet. Not a few of the roots 

 grow deeper, the well-branched tips of some reaching a maximum depth of 

 2.6 feet. A large number of individuals were examined. 



Further studies of this species were made on a well-covered sandhill near 

 Seneca, Nebraska. The plants were in blossom and had flowering stalks 6 to 8 

 inches high. They showed the same root habit as regards widely spreading 

 surface roots and profound branching. However, the working depth was 

 found to be somewhat greater. It averaged 2.8 feet, while a few roots reached 

 a maximum depth of 3.3 feet. The wide lateral spread was found to be 

 constant. 



Several other characteristic sandhills species were excavated and 

 studied in this area, but, since they have also been investigated in 

 other habitats, these data will be given in the chapter on ecads. 



SPECIES EXCAVATED IN HARD LANDS. 



In the preceding pages have been described the species excavated 

 in sandy soil of mixed prairie only. In addition are the root systems 

 of several species which were examined in typical hard lands. These 

 plants were excavated at Colorado Springs and Limon, Colorado, and 

 at the United States dry-land experiment station at Ardmoie, South 

 Dakota (fig. 14). A sufficiently complete account of the vegetation 

 and soil at Colorado Springs has already been given on page 27. At 

 Limon, 70 miles eastward, and under approximately the same precipi- 

 tation, some typical areas of mixed prairie occur. The distribution of 

 vegetation, like the root development of certain crop plants in this 

 area (p. 116), is largely determined by edaphic conditions. Where the 

 soil consists of compact silt-loam, there is a marked expression of the 

 short-grass vegetation, but where it is of a sandier consistency typical 

 mixed prairie occurs. Although considerably overgrazed, the area 

 where roots were excavated was dominated by Stipa comata, Aristida 

 purpurea, and Agropyrum glaucum with Bulbilis dactyloides and Boute- 

 loua gracilis. Numerous other grasses, especially Kceleria cristata, 

 Fesluca octoflora, Sitanion hystrix, and Schedonnardus paniculatus, and 

 the sedge Carex stenophylla were present, together with societies of 

 Psoralea tenuiflora, Astragalus microlobus, Chrysopsis villosa, Gutierrezia 

 sarothrce, Artemisia frigida, Grindelia squarrosa, and Aragallus lambertii. 



