. The ecological relations of roots . Fig. 19.—Senecio aureus oblanceolatu^. inches. All parts of the root system, beginning about 2 inches below the soiland extending to a depth of about 10 inches, are thickly supplied with smalllaterals, usually about mm. in diameter and from to 3 inches inlength. These small laterals often come off in groups of 2 or 3. They arethemselves branched, ending in very minute capillary termini, thus affordinga very excellent system for surface absorption. The roots are white in color,herbaceous, and for roots of this character fairly tough. When cut, small
. The ecological relations of roots . Fig. 19.—Senecio aureus oblanceolatu^. inches. All parts of the root system, beginning about 2 inches below the soiland extending to a depth of about 10 inches, are thickly supplied with smalllaterals, usually about mm. in diameter and from to 3 inches inlength. These small laterals often come off in groups of 2 or 3. They arethemselves branched, ending in very minute capillary termini, thus affordinga very excellent system for surface absorption. The roots are white in color,herbaceous, and for roots of this character fairly tough. When cut, smallamounts of latex exude. Six plants were examined (fig. 20). THE PLAINS ASSOCIATION. 61 Opuntia camanchica.—This Opuntia enjoys a very wide distribution in theplains grassland. Its water requirement seems to be somewhat less than thatof Bouteloua. It is favored in its competition with the grasses by grazing, andits development in great abundance is frequently indicative of overgrazing. A single, carefully selected plant of average
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