DESCRIPTION OF THE COTTON PLANT 9 



character of the soil. After reaching the upper surface 

 of the water-table in the soil, the primary root either 

 ceases to grow or is diverted horizontally. Balls, 1 working 

 with Egyptian cotton, traced a tap-root to a depth of more 

 than seven feet. In a sandy soil and subsoil the South 

 Carolina Station traced well-developed tap-roots to a 

 depth of nearly three feet without coming to their end. 2 

 Conversely, it was found that cotton plants growing 'on 

 heavy clay loam soil very rarely produced well-developed 

 tap-roots more than nine inches in length. Under very 

 unfavorable conditions the tap-roots may be absent. 



The secondary roots branch off laterally from the 

 primary root. They again produce other laterals and this 

 branching process continues until the soil is completely 

 filled with a net-work of copiously branched roots to a 

 depth that varies from two to eight inches. The lateral 

 roots begin to grow below the surface of the soil at a 

 depth varying from one-half inch to three inches. If the 

 soil is moist they may come almost to the surface a short 

 distance from the plant. In almost any soil the secondary 

 roots develop sufficiently near the surface to be injured by 

 deep cultivation. After growing in a lateral direction for a 

 distance varying from two to three feet, some of the 

 secondary roots grow abruptly downward to a depth of 

 three or more feet, presumably for the purpose of aiding the 

 plant in securing moisture. 



The absorptive power of the secondary roots is due 

 largely to the root-hairs. These root-hairs are microscopic 

 in size and never develop into true roots. They comprise 

 an infinite number of delicate out-growths of the surface 

 cells of the root, forming thin-walled hairs. They are 



1 Balls, W. L., "The Cotton Plant in Egypt," p. 33. 



2 South Carolina Station Bulletin No. 7, 1892. 



