THE HALF-GRAVEL-SLIDE COMMUNITY. 



93 



to only 6 or 8 inches on either side of the base of the plant. The roots are 

 hght tan in color and show considerable tensile strength (fig. 38). 



Rubus deliciosus. — This plant is one of the most important of the shrubs 

 of the half-gravel-slide. With Opulaster and certain others it forms the 

 transition stage to forest. 



Three specimens were examined which were so similar that only one will be 

 described. This plant arose from a tap-root 15 mm. in diameter. It had 3 

 main branches, two of which reached a height of 20 inches. At a depth of 3 

 inches the tap-root gave off 2 laterals, 2 and 3 mm. in diameter respectively. 

 The smaller of these ran off almost horizontally to a distance of 20 inches, 

 giving off great numbers of much-branched laterals, the termini being almost 



Fig. 38. — SoUdago oreophila, showing wide-spreading lateral and deep central roots. 



hairhke and reaching a depth of over 20 inches (plate 25, c). The larger 

 lateral ran off in the opposite direction to a distance of more than 2 feet, 

 branching repeatedly and ending in clusters of rootlets only 4 inches below 

 the soil surface. On the first 5 inches of the tap several other smaller rootlets 

 occurred, while at 6 inches depth the root divided into 2 equal parts about 6 

 mni. in diameter. One of these soon rebranched, while all ran off more or less 

 horizontally or obliquely, some to a distance of approximately 3 feet from the 

 base of the plant. The maximum depth did not exceed 36 inches. These 

 roots branched repeatedly into both large and small laterals, those running 

 horizontally being characterized by a multitude of shorter, minutely branched, 

 often vertically descending rootlets. Thus the plant is provided with an 



