320 Journal of Agricultural Research voi. vi, no. 9 



Stage III. — In 1914 the roots of the three plants were isolated about 

 the first of August, 10 weeks from the time of planting. The corn at this 

 stage was shooting and had a height of ^}4 feet, while Blackhull kafir 

 was heading and stood 4 feet high. The seed of the Dwarf milo was in 

 the milk stage, and the plant had reached a height of 3 feet. 



The greatest depth of root penetration at this stage was 4 feet for all 

 the plants. The maximum lateral extent of the roots of corn was 2j/^ 

 feet, while the roots of both Blackhull kafir and* Dwarf milo showed a 

 maximum horizontal extent of 3^^ feet (PI. XL, fig. 2). 



The roots at this stage were isolated on July 17, 191 5, when the plants 

 had reached the same age at which they were examined the previous 

 year. The corn at this date stood 5 feet high, and the tassel was just 

 beginning to show. Blackhull kafir stood 3^^ feet high and had seven 

 fully and five partially unfolded leaves. The Dwarf milo was blooming 

 and had a height of 3 feet. 



The maximum depth and lateral extent of the roots at this stage 

 was found to be approximately the same for all three plants. The 

 greatest depth of the roots was 43^ feet, while the greatest extent in a 

 horizontal direction was approxim^ately 37^ feet. 



Stage IV. — The root systems at this stage were isolated on August 

 25, 1 914, when the plants were 13 weeks old. The com had reached a 

 height of 6 feet and the grain was in a glazed condition. The seed 

 of Blackhull kafir was in the milk stage and the plants Avhich stood 

 5 feet high had reached their maximum vegetative growth. The seed 

 of the Dwarf milo was fully ripe, and the plants had made little if any 

 growth since the previous stage (PI. XLIV, fig. 2). 



The roots of all three plants were found to reach a maximum depth 

 of 6 feet, while the greatest lateral extent for all three was between 

 3 and 4 feet (PI. XL, fig. i). 



In 1 91 5 the plants had not reached their full vegetative growth until 

 September 3, and even at that date they were not nearly as mature 

 as those examined at the same age in 1914. The corn was 7 feet high, 

 and the grain was in the early milk stage. Blackhull kafir was in 

 bloom and had a height of 6 feet, while the grain of the Dwarf milo 

 was in the milk stage and the plants stood 2>% feet high. 



The maximum depth of the root systems was 6 feet for each plant, while 

 while the maximum extent horizontally for each was 373 feet (Pi. XLI, 

 fig. 1,2). 



Both the primary and secondary roots of Dwarf milo and Blackhull 

 kafir at all stages of growth were more fibrous than those of the corn. 

 The length of the secondary roots was found to be approximately the 

 same for the three plants at any given stage of growth. The secondary 

 roots of kafir and Dwarf milo broke so easily in the washing process that 

 it was almost impossible to obtain them intact from the soil which was 

 used in this experiment (Pi. XLII, fig. 1,2). 



