V. ECADS. 



The preceding pages have dealt with species the roots of which were 

 undescribed and were excavated in only one or two places. The present 

 chapter treats of plants, most of which are dominants, that have been 

 examined in many places and under widely varying habitats from the 

 Missouri River to the Rocky Mountains. These include species 

 characteristic of sandhills, mixed prairies, and short-grass plains. 



Bulbilis dactyloides. — This dominant of short-grass plains has a very wide 

 distribution. It makes up much of the lower layer in mixed-prairie vegetation 

 and occurs as alternes far eastward in the true prairies. Perhaps no other 

 grass of the western plains, except grama, is better known for its valuable 

 characteristics as a pasture grass ; while for winter forage it has no equal. 



In 1918 the roots of a dozen plants of this species were examined in a low- 

 prairie area on alluvial soil near Lincoln. These fine roots scarcely spread at 

 all laterally, but formed a dense mat to a depth of 1 to 1.5 feet. Below this 

 depth they become less numerous, so that the deeper soils are sparsely occupied 

 However, many roots occurred at 4.5 feet, and numerous others continued 

 vertically downward to a maximum depth of 5 to over 6 feet, and in one of the 

 trenches in gumbo soil to the ground-water level. This root behavior was so 

 different from that reported by Ten Eyck (1904), in eastern Kansas, where 

 "the roots are numerous but do not penetrate deeply into the soil," and by 

 Shantz (1911) in Colorado, that careful examinations of the root habits of 

 this dominant were made at eight different stations. Shantz's finding that 

 "almost the entire root system of the short-grasses {Bulbilis dactyloides and 

 Bouteloua gracilis) is limited to the first 18 inches of soil" was not confirmed 

 in any instance. In fact, it will be shown that both of these xerophytic 

 species, in addition to having a splendid absorbing system near the surface, 

 are also deeply rooted. 



Bidbilis roots were excavated in the short-grass plains near Yuma, Colorado. 

 Here the soil consists of a chocolate-brown silt-loam, which is very hard and 

 breaks out in lumps, showing more or less of a columnar structure. At a 

 depth of 2.8 feet (in the trenches where the roots were excavated) it became 

 lighter in color, but little harder in texture. This whitish-colored la}^er was 8 

 to 10 inches thick. Below it and extending to the maximum depth excavated 

 (8 feet), the soil was much looser and consisted of yellowish clay, silt, and very 

 fine sand, which at a depth of 7 feet became almost ashy 

 in consistency. Soil samples taken in duplicate at the two 

 ends of the long trench and to a depth of 8 feet on July 17, 

 1919 (table 6), show that the water-content throughout 

 was exceedingly low. 



The vegetation is of the closed mat type (plate 9, a) 

 and quite unlike that at Sterling, but very similar to that 

 described at Burlington, Colorado (p. 74 and plate 2). 

 Buffalo grass was far more abundant than grama. 



The short, frequently branched rhizomes lie mostly 

 within the first inch of soil. They are only 1.5 to 2.5 

 mm. in diameter, brittle and woody, and usually not over 

 0.5 to 2.5 inches in length. The stolons are usually very 

 much longer. From the base of the plant clumps the roots 

 72 



Table 6. 



