The History and Relationships of the 

 World's Cottons 



By Sir Joseph Hutchinson 



Professor of Agriculture, University of Cambridge, England 



Students of the cotton plant enjoy the enormous advantage of a 

 comprehensive work of reference: in 1907 Sir George Watt [27] ^ 

 set out all that was then known of the botany of the plant and much 

 of its agricultural history. Modern work on the crop began with 

 S. C. Harland's analysis [11] of the nature of the species distinctions 

 among the cultivated cottons, and led to studies of their origin and 

 evolutionary history [15, 19]. Harland's work was, in addition, a 

 major contribution to genetics. 



Harland's study of the genetic nature of the species distinction led 

 to the acceptance of four, and only four, species to embrace the whole 

 vast diversity of the cultivated cottons. Between these four the pri- 

 mary distinction is in chromosome nmiiber. Two species, Gossypiwn 

 herbaceum and G. arhoremn^ are diploid, with n=13 chromosomes; 

 they are confined to tropical and subtropical regions of the Old 

 World. Two species, G. hirsutum and G. harhadense^ are tetraploid, 

 with n=26 chromosomes, and it has been shown that, of this comple- 

 ment, half is homologous with the complement of the Old World dip- 

 loids, and half with the complement of species of the genus growing 

 wild in the New World. The tetraploid species were confined to the 

 New World until they were spread, along with other New World crop 

 plants, over the Old World in recent times. 



These four species all bear lint hairs on the seed. The wild species 

 of the genus also bear hairs on the seed, but these are short and 

 scanty, and of a type that could not be spun. The term "cotton" is 

 properly restricted to the lint-bearing species. 



The commercial cottons of the present day are almost all short-term 

 annual plants. They belong to a genus of peremiial shrubs, and the 

 primitive forms of the cultivated species are i:>erennial shrubs; the 



1 Reprinted by permisHion from Endeavour, vol. 21, No. 81, January 1962. 

 * Figures in brackets refer to list of references at end of article. 



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