12 BULLETIN 332, U. S. DEPARTMENT OF AGRICULTURE. 



UNSATISFACTORY CHARACTER OF THE ORIGINAL STOCKS. 



During the earlier years of the breeding work in Arizona the be- 

 havior of the plants was very unpromising. They made an extremely 

 rank growth, but were relatively unfruitful and late in maturing. 

 The bolls were small and often opened imperfectly. There was also 

 a pronounced lack of uniformity in the imported stocks and in the 

 strains which were first selected from them. 1 



Mr. O. F. Cook, as a result of observations upon Egyptian varieties 

 grown in Arizona from newly imported seed, reached the conclusion 

 that the difficulty in obtaining uniformity was largely attributable 

 to the presence among the Egyptian stocks of a very different and 

 inferior type of cotton, the Hindi, the resulting cross-pollination 

 haAdng led to serious contamination of the Egyptian varieties. The 

 matter seemed of sufficient importance to warrant an investigation 

 in Egypt by Mr. Cook in 1910. The degree of Hindi contamination 

 observed in that country was surprisingly great. 2 



Nearly every cotton field inspected was found to contain Hindi 

 plants, and in some fields as many as 20 per cent of the plants were 

 of the Hindi type. The percentage of pure Hindi plants does not 

 represent the full extent of the damage, since this type crosses readily 

 with the Egyptian cotton and the final result is a series of hybrids 

 possessing in varying proportions the characters of each parent. 

 Commencing with a mixed population of this sort, a uniform cotton 

 can be developed only by the selection of an individual plant which 

 possesses the characters desired and which breeds true, thus permit- 

 ting the segregation of a pure stock. 



Even if there were no Hindi cotton in Egypt, the conditions would 

 be unfavorable for the maintenance of uniform varieties, since a num- 

 ber of distinct types of Egyptian cotton are grown, often in adja- 

 cent fields, and the pollen is readily carried from field to field by 

 insects, leading to the production of interparietal hybrids. Further- 

 more, until very recently no adequate precautions were taken to avoid 

 the mixing of seeds at the gins. 



DEVELOPMENT OF MORE UNIFORM VARIETIES. 



Success in the effort to obtain a variety which could safely be rec- 

 ommended for commercial production was not attained until the 

 variety called " Yuma " was segregated in 1908. 3 Although selected 



1 Cook, O. P., McLachlan, Argyle, and Meade, R. M. A study of diversity in Egyptian 

 cotton. U. S. Dept. Agr., Bur. Plant Indus. Bui. 156, 60 p., 6 pi. 1909. 



2 Cook, O. P. Hindi cotton in Egypt. U. S. Dept. Agr., Bur. Plant Indus. Bui. 210, 

 58 p., 6 pi. 1911. 



3 Por a more complete description of this variety and a more detailed account of its 

 history, see Kearney, T. H., Breeding new types of Egyptian cotton, U. S. Dept. Agr., 

 Bur. Plant Indus. Bui. 200, 39 p., 4 pi., 1910. See also Kearney, T. H., Mutation in 

 Egyptian cotton, in Jour. Agr. Research, v. 2, no. 4, p. 287-302, pi. 17-25, 1914. 



