Investigations at Peru, Nebraska. 



21 



Corn, Zea mays indentata. 



The corn plat was plowed April 4 to a depth of 4 inches and harrowed 

 immediately afterward. It was harrowed again May 5 to keep it free from 

 weeds, and on May 9 was planted with Iowa Silver Mine corn. This is a 

 large, rather late maturing variety. Before planting, the plat was marked 

 off in rows 3 feet apart and the seed was drilled along the marks without 

 furrowing. The kernels were planted 3.5 inches deep and 1.4 feet apart in 

 the rows. That part of the plat in which the excavations were made was 

 cultivated very shallow with a hoe so as not to disturb the roots. It was 

 hoed three times, on May 31, June 16, and July 9, respectively. 



The first examination of the root system was made June 14, 36 days after 

 planting. The height of the crop averaged from 10 to 14 inches and the 

 seventh and eighth leaves were just unfolding. The stand was very uniform. 

 In this early stage of growth it has a distinctive surface system of roots. 



Fig. 7. — Root system of Iowa Silver Mine corn 36 days old. 



Of the several plants examined no root approximating the position of a tap- 

 root was found. Whether originating from the hypocotyl or from a node 

 above, the roots took a course parallel or almost parallel with the surface 

 of the soil. In this manner they ran out in all directions from the points 

 of origin. The number of roots varied from 10 to 15; they were about 1.5 

 mm. in diameter, and ranged in length from 0.1 to 2.6 feet. They ended 

 from 0.2 to 1.3 feet below the surface (fig. 7). Throughout their length, 

 excepting the last 8 to 12 inches, all the roots were profusely branched and 

 as many as 33 rootlets were counted on a single inch. The branches varied 

 from a few millimeters to 4 inches in length and were themselves rebranched. 



*This period had been very favorable for plant growth. Although May was 

 somewhat dry, the precipitation during the first half of June was greater 

 than normal. The available water-content to a depth of a foot averaged 



