II. ROOT SYSTEMS OF TRUE-PRAIRIE SPECIES. 



During 1919, studies of the root systems of dominant and subdomi- 

 nant true prairie species were made at the base station on both high 

 and low prairie areas near Lincoln, Nebraska. In addition to further 

 studies of certain species, the root systems of which have already been 

 described (Weaver, 1919), the following plants were excavated: 



Aster multiflorus. — This autumnal subdominant, while occurring through- 

 out much of the grassland formation, reaches its greatest abundance and best 

 development in the true prairie. Here it is conspicuous from the time its 

 many white or purplish flowers begin to blossom in August until late in Octo- 

 ber. Clumps of this rather bushy plant are connected by tough, woody 

 rhizomes 4 or 5 mm. in diameter and from an inch to over 8 inches in length. 

 Frequently they are short and the plants densely matted together. The 

 plant is supplied with numerous fibrous roots usually 2 mm. or less in diameter. 

 While some descend rather vertically downward, more often they run obliquely 

 and at a depth of a foot may be 1.5 feet from the base of the plant. This 

 criss-crossing of the roots underneath a clump is often quite marked, the soil 

 being filled not only with the larger roots which penetrate deeply, but also 

 with numerous finer and shorter ones which absorb mostly or entirely in the 

 surface foot of soil. They are fight tan in color, very tough and wiry, and the 

 larger ones give off few branches near the soil surface. Throughout their 

 course to a working depth of 5 feet they give off branches from time to time 

 (fig. 1) . These are sometimes 10 or more inches in length, but more frequently 

 they are 0.5 to only 2 or 3 inches long. In general they are poorly rebranched. 

 The production of laterals, however, is quite variable. Some roots are fur- 

 nished at intervals of 0.2 to 0.5 inch with rebranched laterals over an inch in 

 length, while others, especially near the tip, run for distances of several inches 

 without branching. However, these unbranched portions are often densely 

 covered with root-hairs. Several roots ended in the seventh and eighth foot 

 of soil. The tips are poorly branched. The root system as a whole is deep- 

 seated and very little provision is made for surface absorption. 



Solidago missouriensis. — This goldenrod is of considerable importance in 

 the structure of grassland vegetation and is widely distributed. It forms 

 autumnal societies in true prairie and mixed prairie from Washington to 

 Manitoba, extending southward to Texas. It propagates by woody rhizomes 

 from 3 to 8 mm. in diameter and from 2 to more than 12 inches in length. 

 From the base of the clump and along the rhizomes arise clusters of roots 

 which are 0.5 to 3 mm. in diameter (fig. 2). Many of these are relatively 

 short, branch repeatedly, and end in the first foot or two of soil. The larger, 

 white, cord-like roots descend laxly and obliquely, seldom at angles of less 

 than 20 or 30 degrees with the horizontal. Some run obliquely a few inches 

 from the rhizome and then penetrate vertically downward. In fact, the root 

 spread is only 12 to 20 inches from the base of the plant. Below the first foot 

 the roots frequently run for several inches without giving off a single lateral 

 or at best only rarely an unbranched rootlet not over a 0.5 inch long. Others 

 give rise, at rather regular intervals of 0.2 to 1 inch, to horizontal laterals a 

 centimeter or less in length and unbranched, but rarely to branched rootlets 

 with a length of 2 to 3 inches. In the harder loess soil, below 4 feet, many of 

 the roots are more or less crinkled. Even at 5 feet many of the larger ones 

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