30 HINDI COTTON IN EGYPT. 



Coherence of characters is not confined to Hindi hybrids, but 

 apparently has to be reckoned with in any attempt to combine the 

 characters of different types of cotton. The phenomenon was first 

 recognized and described in the study of Egyptian-Upland hybrids 

 in Texas and Arizona. It differs from correlation in affecting whole 

 groups of characters instead of only two or three. Thus a general 

 correlation may be said to run through many different types of cot- 

 ton — between the shape of the boll and the length of the lint or 

 between the color of the lint and its strength. Correlation refers pri- 

 marily to the fact that certain characters tend to vary together, one 

 increasing or diminishing in relation with another. The fact that 

 the weiiiht of ears of corn increases with their length is reckoned as 

 a correlation. Coherence refers to the expression of characters in 

 hybrids. It denotes a condition in which characters derived from 

 the same parent remain together in expression instead of being 

 expressed in chance combinations as in Mendelian hybrids. 



Correlations often appear entirely arbitrary, unless they are merely 

 mathematical expressions, as in the case of the corn ears. From the 

 mathematical standjjoint it seems impossible to understand why long 

 fibers should not be packed into round bolls as well as into pointed 

 bolls or why brown fibers should not grow as long as white fibers. 

 But after the tendency to coherence of much larger groups of char- 

 acters has been recognized as a fact correlations appear somewhat 

 less mysterious. The general association of longer lint with more 

 pointed bolls in any particular type of cotton ma}' be connected with 

 the other general fact that the long-linted types of cotton have more 

 gradually tapering bolls than short-linted types of cotton. Coher- 

 ence implies that the expression or nonexpression of one character 

 may determine whether other characters shall be patent or latent. 



A striking example of coherence of characters was observed in 

 Egypt in a block of hybrids made by Mr. F. Fletcher, director of 

 the School of Agi'iculture at Gizeh, between an American Upland 

 variety called Jackson's Limbless and an Egyptian variety called 

 Voltos, somewhat similar to Nubari, Voltos being the male parent. 

 In addition to many other courtesies of hospitality Mr. Fletcher 

 most generously insisted upon a full use of his interesting series of 

 experimental plantings of cotton at Gizeh, which yielded many in- 

 teresting facts with special relation to problems of diversity. 



Instead of the usual tendency of some of the Egyptian traits to 

 predominate in the first generation, this lot of hybrids showed an 

 unusually definite expression of the U{)land characters. Very few 

 of the plants would have been taken for Egyptian cotton, even on 

 casual examination, and none of them showed any close approxima- 

 tion to the Egyptian type. On the other hand, a considerable pro- 

 portion of the phinls adhered very closely to the characters of the 



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