THE SANDHILLS SUBCLIMAX. 



75 



surface laterals with their large nodules 1 mm. wide and 2 to 3 mm. long, 

 their wide lateral spread, sometimes to a distance of 2.5 feet, as well as the 

 abundant system of well-branched absorbing laterals. Laterals of various 

 sizes, and often with a spread of more than a foot, come off at all depths to 

 near the tip. Characteristically these run off somewhat horizontally and then 

 turn down rather abruptly. All of the termini are furnished with a profuse 

 network of finely branched rootlets. In color the roots vary from light yellow 

 and deep orange to brick-red. In diameter the tap was variable, lower por- 

 tions often being of larger size than other parts above. 



Fig. 27. — Root system of Petalostemon villosus. 



Gilia longiflora. — Three plants of this annual, growing on a well-covered 

 sandhill, were examined, all were mature and in full bloom; their underground 

 system started with a strong tap-root, varying in size from 7 to 12 mm. in 

 diameter. The tap penetrates almost vertically downward, tapering very 

 rapidly until, at a point 6 inches below the surface, it is usually not more than 

 3 mm. in diameter. From this depth it tapers more gradually, pursuing a 

 kinky and tortuous course downward through the sandy soil to a maximum 

 depth of 40 to 50 inches (fig. 28). The most marked characteristic of these 

 tap-roots is the remarkable number of both large and small laterals thrown 

 off within the first 2 to 10 inches of soil. From 8 to 14 of these are often found, 



