12 BULLETIN 742, U. S. DEPARTMENT OF AGRICULTURE. 
a pronounced lack of uniformity in the imported stocks and in the 
strains which were first selected from them. : 
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 
having 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.? 
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 intervarietal 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.° Although selected 
from a stock of Mit Afifi, the Yuma cotton is very distinct from that 
variety in the characters of the plants and of the fiber. The lint 
averages 14 inches in length and has the pale pinkish buff color of 
the Jannovitch rather than the deeper buff color of the Mit Afifi. 
The lint percentage averages about 28. 
1 Cook, O. F., McLachlan, Argyle, and Meade, R. M. A study of diversity in Egyptian 
cotton. U.S. Dept. Agr., Bur. Plant Indus. Bul. 156, 60 p., 6 pl. 1909. 
2Cook, O. F. Hindi cotton in Egypt. U.S. Dept. Agr., Bur. Plant Indus. Bul. 210, 
HOD Opie wl Oat 
3’ For 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. Bul. 200, 39 p., 4 pl., 1910. The Yuma and Pima varieties are also 
described by Mr. Kearney in an article entitled ‘‘ Mutation in Egyptian cotton,” in Jour. 
Agr. Research, v. 2, no. 4, p. 287-802, pl. 17-25, 1914, 
