THE FOREST COMMUNITY. 



101 



single plant. For the most part the roots extend in a direction aknost par- 

 allel with the surface of the soil. The depth at which they lie varies from 

 2 to 8 inches and the maximmn lateral extent is 14 inches. Relatively a 

 very few of the roots take a more vertical or slightly oblique downward 

 course, but none reach a depth below 18 inches. The main roots are a milli- 

 meter or less in diameter. Throughout the course of the roots an elaborate 

 system of branching occurs. The branches ramify to the third and fourth 

 order, and vary in length from a few millimeters to 3 or 4 inches. Near their 

 extremities the main roots are so well branched and divided that the tip con- 

 sists of a brush-like mat of fine rootlets (fig. 43). 



Fig. 43. — Thalictrum fendleri. 



Erigeron asper.— This plant forms fine societies in the dense shade of the 

 spruce-fir forest. The individual clumps are connected by means of branched 

 surface rhizomes, seldom over and often less than 2 mm. m diameter, which 

 usually do not lie at a depth beyond 2 inches. From the base of the plant in 

 particular, as well as along the rhizome, a well-developed system of rather 

 fibrous roots arises. The largest of these do not exceed a millimeter in diameter 

 and are usually much smaller. While some of these penetrate to maximum 

 depths of 26 to 30 inches, the first 18 inches of soil and especially the first 6 

 inches are thoroughly filled with the hairhke and profusely branched rootlets. 

 Frequently these branches, which arise in great abundance all along the main 

 roots, run off obliquely and even almost horizontally to distances of 5 to 10 

 inchesjrom the base of the plant (fig. 44). 



^^ Erigeron macranthus.— This plant, which is not infrequent in openings in 

 the forest, propagates by means of rather coarse rhizomes often about 5 imn. 

 in diameter and several inches in length. From the base of the plant and from 



