THE PRAIRIES. 



11 



Solidago canadensis. — ^This abundant prairie goldenrod propagates by 

 means of strong woody rhizomes, a centimeter or less in diameter, which run 

 horizontally about 2 inches below the soil surface. As in S. rigida, the roots 

 are fibrous. They are about 1 to 2 mm. in diameter and pale yellow in color. 

 They descend rather vertically into the soil. From these abundant roots 

 numerous laterals are sent off, beginning just below the surface and con- 

 tinuing to a depth of from 9 to 10 feet. However, the main roots keep their 

 identity throughout their course and are very poorly branched throughout 

 the last foot. Thus the soil was well occupied with the roots of this species 

 and few other roots were found in the Solidago area. Eleven plants were 

 examined, most of which gave a maximum root depth of 10.5 feet, while one 

 reached 11 feet. 



Silphium laciniatum. — ^The wide distribution of this coarse perennial 

 prairie plant is well known. It has a large, fleshy, deep tap-root. The root 

 diameter just below the multicipital crown, which gives off numerous shoots, 

 varied from 1 to 2 inches in the 5 plants examined. The tap-root descends 

 vertically and tapers so rapidly that at 3 feet it may be only 0.5 inch in 

 diameter (plate 7, a). It pursues this general vertical direction to a maximum 

 depth of from 9 feet to 13 feet 8 inches, the last 2 or 3 feet of its course being 

 somewhat tortuous. The whole root is a dark reddish-brown in color, the 

 cortex of the first 18 inches being distinctly ridged and wrinkled. Scattered 

 laterals, 2 mm. or less in diameter and from 6 to 18 inches long, are present 

 on this upper portion of the root. There are relatively few large laterals. 

 These frequently run off horizontally for a distance of 3 or 4 feet and then 

 turn downward. The deeper roots are also fleshy and brittle and end rather 

 abruptly; usually they are freely branched. 



Amorpha canescens. — This half-shrub is a characteristic subdominant of 

 the summer aspect on the prairies of eastern Nebraska. Late in June it 

 begins to blossom and throughout July its leaden color gives tone to the 

 landscape. This perennial legume has a very extensive, woody root system 

 which reaches depths of 6.5 to 7.5 feet. While some of the plants examined 

 branched into large lateral roots just below the enlarged knotty crown, others 

 sent vertically downward a single tap-root. These extremely tough woody 

 roots have a maximum diameter of more than a centimeter. Frequently, 

 large laterals run off horizontally at a depth of only 4 to 6 inches below the 

 soil surface to a distance of 2.5 to 3 feet before they begin their downward 

 course (plate 7, b) . Few laterals are given off until the roots reach a depth of 

 from 2 to 3 feet; then the roots by dividing become much finer and branch 

 quite profusely. The terminal branches are very fine, almost threadlike. 

 The roots are cinnamon-brown in color; the cortex is smooth, except on older 

 portions, where it is finely scaly. Five plants were examined. 



Helianthus rigidus. — ^This sunflower, common on Nebraska prairies, 

 propagates by strong rhizomes, from which arise abundant fibrous roots only 

 1 to 1.5 mm. in diameter. These reach a depth of about 50 inches. 



Brauneria pallida. — Only 2 plants were examined. Both had strong, 

 vertically descending tap-roots which reached depths of 51 and 66 inches 

 respectively. These roots were 1 or 2 cm. in diameter. They were poorly 

 supplied with branches, only 3 or 4 short, weak laterals occurring on each root. 

 Even the tip is unbranched. They are woody, and are chocolate-brown in color. 



Petalostemon candidus. — ^Both this plant and Brauneria are common and 

 often very abundant prairie species. Like Brauneria, it has a strong, deep, 

 rather poorly branched tap-root. Of the two specimens examined the smaller 



