CHAPTER VII 



NATURAL CROSSING 



WHEN the author first began his researches it was gener- 

 ally assumed that cotton was self-fertilised, and the only 

 precise statement to the contrary was that of Webber, 

 who had found 5 per cent, natural crossing between 

 adjacent rows of distinct varieties. At the present day 

 the seriousness of the crossing error has been demonstrated 

 and admitted in many countries,* but the importance of 

 the subject does not end with this conversion. 



Field conditions. The author's first concern was to 

 investigate the amount of crossing which had taken place 

 in field crop during 1904 by examining the offspring from 

 random single bolls of that year. 5 ' 8 It was found that when 

 a plant did not give uniform offspring, resembling itself, 

 the difference of the offspring from the parent might be of 

 two kinds. 



In one case the offspring, or some of them, bore 

 characters which were dominant over those of the parent ; 

 thus a 40 mm. lint might be derived from a 25 mm. lint; 

 the presumption here was that all or some of the parent 

 ovules had been crossed in the previous year by pollen 

 from a loug-linted plant. This was the rarer case, which 

 in itself defines the amount of natural crossing, if we take 



* Notably Lenke, H. M. (1), (4), and Allard, H. A. 

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