102 



THE ECOLOGICAL RELATIONS OF ROOTS. 



the rhizomes arise great clusters of fibrous roots from 3 to 4 mm. to only 0.5 

 mm. in diameter. While many of these run rather vertically downward, so 

 that some of the longer ones reach depths of 40 inches, others spread laterally 

 to a distance of 14 to 18 inches and reach depths of only 4 to 12 inches. Thus 

 the soil for a distance of more than a foot on either side of the plant and to a 

 depth of 2 or 3 feet i? well supplied with these fibrous roots. The branching 

 of the root is abnost identical with that of Erigeron asper (fig. 44), with which 

 this species seems to intergrade. 



Fig. 44. — Rhizome and roots of Erigeron 

 asper. 



Fig. 46. — Allium cernuum. 



Fragaria virginiana. — Fragaria forms societies rather extensively on the 

 forest floor, even in the dense shade of spruce seedlings. In addition to the 

 long, slender stolons, it is furnished with rhizomes only 3 to 5 mm. in diameter 

 but often several inches long. From these arise the dark-colored fibrous roots 

 a millimeter or less in diameter. There are usually 6 to 10 of these on an inch 

 of the rhizome. Many of them pursue an oblique course to a lateral distance 

 of 4 to 10 inches from the base of the plant, where they reach a depth of 4 to 

 12 inches. Others penetrate more vertically downward to a maximum depth 

 of 12 to 14 inches. While the first inch of the roots below the superficial 

 rhizomes is rather destitute of branches, below this depth, especially in the 

 last 6 to 8 inches, the roots are supplied with an abundance of fine rebranched 

 termini ranging in length from 1 to 5 cm. (fig. 45). 



