CHAPTER XIII 

 COTTON AND SORGHUM 1 



Little is definitely known of the antiquity and origin of cotton. 

 Evidence has been obtained which indicates that it was culti- 

 vated in India in 1,500 B.C. and in Egypt 1,300 years later. 

 Species of cotton are indigenous both to tropical America and to 

 India. Because of the extent of natural crossing (5-13 per cent.) 

 (Balls, 1912) the difficulties of studying inheritance and of carry- 

 ing on practical breeding operations are very great. It seems 

 reasonable, however, to consider this crop in the self-fertilized 

 group, as the extent of crossing leads to the belief that continued 

 self-fertilization will not give harmful results. It also seems 

 reasonable to conclude that deterioration in a selected variety is 

 largely the result of natural crossing. Methods of pedigreed seed 

 production should, therefore, be developed to their highest 

 possible efficiency. 



Classification and Inheritance. Gossypium contains several 

 species. The two species of cotton grown commercially in the 

 United States, upland (G. hirsutum) and sea-island (G. barbadense) 

 cross readily with each other. The varieties cultivated in Egypt 

 also belong to G. barbadense, but in India the forms derived from 

 G. herbaceum are chiefly grown. Webber (1905) was unable to 

 cross Aiden cotton which he classified as G. herbaceum, with either 

 sea-island or upland varieties. The commercial value of cotton 

 and the separation into the above species groups is largely deter- 

 mined by three characteristics of the fiber: namely, length, 

 tensile strength, and fineness. Other morphological characters 

 have been used in classification. These are presence or absence 

 of fuzz on the seed, color of fiber and flower, form of boll and 

 general habit of growth. The wide range of environmental or 

 place effect exhibited by the cotton plant generally, as well as 

 heterozygosis due to natural crossing, has made clear-cut classi- 

 fication difficult. G. hirsutum is a vigorous annual plant with a 



1 While sorghum is botanically one of the grasses, yet from the stand- 

 point of the breeder it is better treated with the self-fertilized group of 

 crop plants. 



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