134 ROOT DEVELOPMENT IN THE GRASSLAND FORMATION. 



examined. But on August 18, when the plants in the lower plats were nearly 

 4 months old, the root development was again recorded. At this time the grass 

 was 8 to 10 inches in height, but had sent up no flowering stalks. The roots had 

 a working depth of 3 feet, although some penetrated 0.7 to 1 foot deeper. To 

 a depth of 1.5 feet the soil was quite filled with great masses of the brown roots, 

 which are only slightly less abundant at 2 feet. They are very fine, the largest 

 being scarcely a millimeter in diameter, while many are only one-fourth that 

 size. They originate from the base of the plant in great numbers, 6 to 24 or 

 even more from a single stem. While most of the roots pursue a course some- 

 what obliquely to almost vertically downward, others spread laterally more or 

 less parallel with the soil surface or obliquely outward 3 to 6 inches before turn- 

 ing downward. They are exceedingly well furnished with threadlike laterals 

 ranging from a few millimeters to several inches in length, all of which are 

 branched and profusely rebranched, ending in hairlike termini. Many of the 

 roots did not reach the general working level; others penetrated far beyond. 

 The 6 to 8 inches of root-ends are not so well branched and are hairlike. To 

 insure certainty of maximum depth, as usual the trench was undercut 6 to 12 

 inches below the deepest roots. 



Oats (A vena sativa).— The roots were first examined on June 12, which was 

 49 days after the crop was planted. At the lower station the plants had 

 reached an average height of 1.8 feet. The roots were abundant to a depth of 

 2.3 feet, while a very few penetrated to the maximum depth of 3.3 feet. At 

 the upland station the plants averaged 1.3 feet in height. They had a working 

 depth of 2.1 feet and a maximum penetration of 2.8 feet. A description of the 

 mature plants has been given on page 102. At the lower station they reached 

 a height of 3 feet at maturity, at the upper station only 2 feet. At the lower 

 station the working depth and maximum depth were 2.8 and 3.4 feet respec- 

 tively, while they were 3.1 and 4.1 feet on the upland soil. 



Sorghum (Andropogon sorghum).— The plats of sorghum, of the Black 

 Amber variety of the "sorgo" group, which were planted on May 27, were 

 given a careful examination 3 months later, on August 26. On both sites the 

 crop was thick. In the lower plats it averaged 4.4 feet in height, while some 

 stalks were 4.6 feet tall and had a maximum diameter of 12 mm. The plants 

 were all in seed. The sorghum on the upland was slightly above 3 feet in 

 average height, the largest stalks having a diameter of 10 mm. and a height of 

 4.3 feet. It was in the late flowering and seeding stages. This plant has tough, 

 fibrous roots, 3 or 4 mm. in diameter at their origin and often a millimeter 

 thick at a depth of 4 feet. They are of a grayish white color, those near the 

 surface being strongly tinged with red and the deeper, younger roots glistening 

 white. They originate in large numbers and completely occupy the hard, dry 

 soil beneath the plants. Branches from 0.5 to 3 inches long are exceedingly 

 abundant and are quite well rebranched. In the more mellow surface soil 

 these branches spread somewhat widely in all directions, but in the hard, 

 jointed subsoil the branching was confined largely to the crevices and was in 

 one plane. The abundant, ultimate branches are hairlike, shining-white, and 

 exceedingly delicate. Not infrequently they occur in clusters of 3 to 5 on a 

 millimeter of root-length. Often they form cobweb-like mats covered with 

 root-hairs in the deeper soil crevices. As a whole, the absorbing system of 

 sorghum is very efficient and so well distributed throughout the soil that it can 

 thoroughly exhaust it of its available water for plant growth. In both plats 

 the roots reached a working depth of 4 feet. The maximum root penetration 

 was also the same, about 4.5 to 4.7 feet. It is interesting to note that Miller 

 (1916) found that the root systems of related groups, Blackhull kafir and 



