138 ROOT DEVELOPMENT IN THE GRASSLAND FORMATION. 



They then ran rather straight downward, branching repeatedly. On both the 

 larger and smaller branches tubercles occurred to a depth of about 3 feet. The 

 amount of branching and the extent of the root development of this 

 2.5-months-old plant is shown in figure 38. Plants in the upland soil were 

 not so deeply rooted. Many roots were found at 2.5 feet depth; some pen- 

 etrated about 0.5 foot deeper. 



On August 18 red clover roots were again examined. In the lower plats the 

 plants were 1.1 feet high, some were still blooming, others were developing 

 seed, and all were in a very healthy condition. From 3 to 13 stalks occurred 

 on a plant. Three plants with tap-roots 5 to 7 mm. in diameter were traced 

 to a depth of 4.5 feet. None were found penetrating deeper. The tap-root 

 tapered so rapidly that at 9 inches depth it was only 1 mm. thick. In the 

 surface 8 inches of soil it gave off 10 major branches ranging from 1 to 2 mm. 

 in diameter. These ran off to distances of 4 to 12 inches in a direction either 

 rather parallel with the surface or only slightly obliquely before turning nearly 

 vertically downward. Like the tap-root, they tapered rapidly, some reaching 

 a depth of 3 to 4 feet. In addition to these branches, the 12 inches of the tap- 

 root, and especially the first 6 inches, were covered with a great network of roots 

 only 0.5 mm. or less in diameter but 1 to 7 inches long. Like the larger roots, 

 many of them spread rather laterally in the surface soil. They were poorly 

 rebranched. Below the first foot no large branches occurred, although in 

 some plants it was noted that the tap-root sometimes broke up into two 

 rather equal parts. Short laterals arose throughout the course of the root and 

 only a few millimeters apart to a depth of 3 or 4 feet. These varied in length 

 from only 0.5 inch to several inches. The younger roots are glistening-white 

 and fill the joints of the deeper soil with a network of rootlets. Other roots are 

 more hairlike and run for an inch or two, giving off practically no branches. 

 Near the tip the laterals are very short. The tap-root is prominent through- 

 out and in general has a vertically downward course. 



In the upland plats the plants were 10 inches high and in blossom, but none 

 had formed seed. Their development in every way was poorer than at the 

 lower station. There were fewer stalks per plant and the largest tap-roots 

 were only 5 or 6 mm. in diameter, while on most of them the roots were smaller. 

 Several plants were traced to their greatest depth at 4 feet. None penetrated 

 deeper. The root habit was similar to that described, but the larger laterals 

 were often fewer. 



Hays (1888) gives the development of red clover plants when grown at the 

 experiment station of the University of Minnesota in a "hollow" in rich drift 

 soil of clay, sand, and loam. The roots reached depths at the ages of 1, 2, and 

 5 months of 7, 22, and 68 inches respectively. In all the plants examined the 

 large laterals were very abundant and many were of equal size and penetrated 

 as deeply as the tap-root. 



The development attained by mature root systems of clover plants is in- 

 dicated in the following description. They were excavated in a fine 6-year-old 

 meadow near Wahoo, Nebraska. The deep, fertile, silt-loam was underlaid to 

 a depth of at least 10 feet with a fairly compact loess subsoil. The soil was 

 quite moist throughout. Many of the plants examined had strong tap-roots 

 10 to 12 mm. in diameter, but they tapered off rapidly and at a depth of a foot 

 were seldom more than half this thickness. However, the tap-roots were dom- 

 inant and ran nearly straight downward to depths of 8 or 9 feet. In fact, one 

 root penetrated to the 10-foot level. A great mass of fine rootlets arose from 

 the crown and first few inches of the tap-root, and, running off laterally for 

 distances of 6 to 8 inches, quite filled the surface soil. Also, a few larger 

 branches, ranging from 2 to 3 mm. in diameter, arose in the surface foot of soil 



