ROOT SYSTEMS OF MIXED-PRAIRIE SPECIES. DO 



17 mm. in diameter, but tapered so rapidly that at a depth of 12 inches it was 

 only 2 mm. thick and scarcely as large as some of its laterals. It descended 

 vertically downward, branching into two equal parts at a depth of 2.8 feet. 

 These ran practically parallel to a maximum depth of 6.8 feet. The tap gave 

 off 17 laterals from 1 to 4 mm. in diameter (most of them from 1 to 1.5 mm.) 

 and 20 smaller ones in the surface foot of soil. Most of these ran off parallel 

 with the soil surface and at a depth of only 2 to 10 inches. These roots reach 

 distances of 1.7 to 3 feet or more from the base of the plant, but their course is 

 so tortuous that they are actually often much longer. They may end in the 

 first foot of soil, but usually penetrate deeper. For example, one root with a 

 diameter of 3 mm. ran off laterally at a depth of 0.7 to 1.3 feet for a distance of 



7 feet before turning downward. It tapered so slowly that at the bend, 7 feet 

 from its origin, it was still a millimeter in diameter. Like many others, it 

 reached a depth of 4 feet. The branching is rather poorly developed. The 

 laterals are threadlike, from a millimeter to over 2 inches in length, and 

 scarcely rebranched. They arise only at long intervals, although in places 

 4 to 6 may come off from a single inch of the root. The general tendency of 

 these laterals is to run nearly parallel with the soil surface, although they may 

 descend obliquely and frequently ascend vertically to near the ground-line. 

 Not more than half a dozen roots exceeding 3 inches in length arose below the 

 first foot. The last foot of the tap was fairly well branched, with rather 

 numerous but short unbranched rootlets. Other root systems were very 

 similar, although some had more large and fewer small branches. It is evident 

 that this plant has a root habit well adapted to get most of its water and solutes 

 from the first 3 or 4 feet of soil. 



Commelina virginica. — The day-flower is a rather common component of 

 sandhills vegetation, where it frequently forms societies. Several fine speci- 

 mens, 6 to 8 inches tall, and in full bloom, were examined in a partially re- 

 vegetated blowout. The fleshy roots, which are brown to black in color and 

 2 to 3 mm. in diameter, usually originate at a depth of 4 to 8 inches below the 

 surface of the sand. Mostly 3 to 5 come off from the base of a single plant. 

 They rarely grow vertically downward, but spread out obliquely in such a 

 manner that at depths of 2 to 3.2 feet they are 0.3 to 1 foot horizontally away 

 from their point of origin. For example : one large root reached a depth of 3.2 

 feet, its characteristic whitish blunt tip ending a foot to one side of the plant, 

 while another younger root, only 0.8 foot long, ended at a depth of 0.5 foot. 

 The roots taper slowly and are very brittle near their tips. None was found at 

 depths greater than about 3 feet. Except near the growing ends, they are 

 densely coated with hairs. The branching is only poorly developed. Some 

 roots had no laterals, others had as many as 6, confined mostly to the surface 



8 inches of soil. Some of these delicate tan-colored rootlets run off in the 

 surface soil, perhaps at a depth of only 0.2 foot, to a distance of 1 to 2.3 feet 

 from their origin. They are seldom over a millimeter in diameter, but, like the 

 main roots, taper only slowly. They give off throughout their course great 

 numbers of delicate rebranched laterals from 0.5 to 8 inches in length. These 

 are distributed in the surface soil. As a whole the root system of this species 

 is shallow and especially well adapted for surface absorption. 



Pentstemon angustifolius. — This beard-tongue, like several other members 

 of the genus, is a subdominant of rather wide occurrence in the more stabilized 

 areas of sandhill vegetation. Three plants in fruit were excavated on a grassy 

 hillside. Each had 3 or 4 stalks which reached a height of about a foot. The 

 roots arise from a woody rhizome, usually 2 to 5 inches in length and 4 to 8 

 mm. in diameter. As many as a dozen may originate from a single inch of the 



