9 o THE COTTON PLANT IN EGYPT 



as uniform, since the inequalities smooth themselves out 

 when a sufficiently large number of plants is taken. 



These group limits have been drawn for convenience, and 

 they are perfectly genuine. Nevertheless, the phenomena 

 are mutually interdependent, so that the humblest plot 

 of cotton cannot be understood without a knowledge of 

 Physiology and of Genetics. The subject of Fluctuation 

 forms a neutral ground between these two relative branches 

 of science ; it belongs to both ; physiology explains it, 

 genetics cannot be explained without it. 



The author frequently had occasion to regret the lack 

 of significance in his older heredity experiments, due to 

 lack of fluctuation data as standards, and when these 

 began to accumulate they were found meaningless until 

 the physiology had been studied. 



