1 30 THE COTTON PLANT IN EGYPT CHAP. 



In rare cases we have been able to demonstrate the 

 existence of Mendelian ratios in F 2 , confirmed by the 

 behaviour of later generations. In others we have failed 

 to analyse the F 2 but have dissected the F 3 , where the 

 phenomena were simpler. In others, again, such analysis 

 has been utterly impossible, and we have been obliged to 

 rely on the bare fact that a certain character has "bred 

 true " in the end, though we have been unable to trace the 

 steps of its purification. As a last infirmity, and last 

 resort, we have fallen back on comparisons from year to 

 year in massed data : if the graph for seed-weight in F 2 

 shows certain modes, and if those modes reappear in the 

 graph for all the F 3 plants in the following year, we have 

 a claim to assume that the modes are at least due to 

 a systematic cause and not to accident. 



The data to be quoted are drawn largely from crosses of 

 Egyptian with American Upland, especially from Afifi with 

 Truitt Big Boll (No. 25 2 ), 15 and from Charara with King 

 (No. 255). Other crosses which have been made, but only 

 partially examined through lack of space and labour, are 

 Hindi x Charara, King x Russell, Russell x Charara, and 

 Sultani x King. In the early stages of the work many 

 natural hybrids were examined, which had resulted from 

 natural crossing between Egyptian cottons, while full 

 analysis has been made up to F 2 in an inter-Egyptian cross 

 between Afifi and another Sultani. The phylogenetic 

 relationships of the various parents is doubtful, to say the 

 least. The author has leaned to the designation " inter- 

 specific," but this has been questioned, in view of the 

 cultivated origin of the parents.* Perhaps a description 

 of them as "reputedly inter-specific" would best meet the 

 case. 



The cross of Afifi x Sultani was made with the object 

 of studying some simple examples in place of the. com- 



* See references "Egypt," in Sir G. Watt's Monograph. 



