THE FOREST COMMUNITY. 



103 



Allium cernuum. — This plant is very characteristic of half-gravel-slides, but 

 also occurs rather abundantly in the open portions of the fir forest. The plant 

 was examined in the forest habitat. The bulb, which is usually 12 to 15 mm. 

 in diameter, occurs at a depth of about 2 inches. From its base arises a cluster 

 of 10 to 20, or sometimes more, fibrous roots a millimeter or less in diameter. 

 These spread widely in the surface 6 or 8 inches of soil. Laterals were traced 

 to a horizontal distance of 8 to 12 inches from the base of the bulb, where they 

 ended at a depth of 4 to 8 inches. No roots were found at a greater depth 

 than 10 inches. These glistening white fibrous roots branch freely into 

 laterals from a few centimeters to 4 or 5 inches in length, but these secondary 

 roots are themselves scarcely at all branched (fig. 46) . 



Aralia nudicaulis. — ^This plant is often abundant on the lower slopes of the 

 fir and spruce forests, where it sometimes forms extensive communities. The 

 individuals are connected by a much-branched system of rhizomes, which 

 vary in diameter from 3 to 4 mm. to more than a centimeter. Frequently 

 they He just below the soil surface, but they are quite abundant at all levels 

 and run in all directions and at all angles in the first 18 to 24 inches of soil. 



Fig. 47. — Rhizomes and root system of Aralia nudicaulis. 



As shown in figure 47, there arise from the nodes of the rhizomes rootlets with 

 clusters of well-branched termini, the whole usually not over 2 to 5 cm. long. 

 Often, however, rather well-branched roots 18 to 20 inches in length occur. 

 The direction in which these run depends somewhat upon the depth of the 

 rhizome. If the root arises from a rhizome near the surface it takes a vertical 

 or oblique course downward ; at intermediate depths the roots frequently run 

 off horizontally, while from the deepest rhizomes it is not unusual to find them 

 ascending in an oblique direction toward the surface. As a whole, the root 

 system is rather poorly developed, probably due to the dense shade in which 

 the plant grows. 



Opulaster opulifollus. — This shrub forms a very characteristic under- 

 growth in pine woods as well as in the open fir forest. Indeed, it reaches its 

 best development in the better hght of the chaparral community and dies out 

 almost completely in forests with a closed canopy. Its role in succession is 



