DESCRIPTION OF THE COTTON PLANT 17 



boll. The length of time from the fertilization of the 

 ovules to the production of a mature boll varies from 40 

 to 55 days. The bolls are oval in shape, distinctly pointed 

 at the apex and vary in size from 1.5 to 2.5 inches in length 

 and from 1.25 to 1.75 inches in width. From the base of 

 the boll to the apex, divisions or valves are found, from 

 three to five in number.^ The contents of each valve are 

 called a lock. The bolls of American upland cotton (both 

 long and short staple varieties) usually contain four or 

 five locks. The Alabama Experiment Station, working 

 with upland cotton, has found that bolls with five locks 

 yield more cotton per boll than bolls having only four 

 locks. 



When the boll matures it opens, exposing the seed cotton 

 inside. The opening is caused by the yalves "separating 

 along theiF. central axis and at the same time splitting 

 down the middle of the back." The valve walls after 

 opening are spoken of collectively as the "bur." 



The Texas Station ^ has found that there is a relation 

 between the thickness of the burs and the tendency of the 

 seed cotton to be blown out by winds or beaten out by 

 rains.. If the burs are thin, they curl backward in opening, 

 thus allowing the seed cotton to drop easily. 



17. Ntunber of bolls to the plant. — The factors that 

 determine the number of bolls to the plant are fertility of 

 soil, rain-fall, cUmate, variety, and the structtire of the 

 plant with reference to the arrangement and character 

 of the vegetative and fruiting limbs. Fertile soils, well 

 supplied with moisture, produce plants with a larger num- 

 ber of bolls than do poor, droughty soils. Excessively 

 productive soils, especially as regards nitrogen, often 

 .produce a large amount of vegetative growth at the expense 

 1 Texas Station Bulletin, No. 75. 



