1 68 THE COTTON PLANT IN EGYPT CHAP. 



obviously complex. The seed- weights of the two parents 

 were substantially the same, being 0'085 for the American, 

 and 0'095 for the Egyptian. The weight of the Fj seed 

 was 0145. Thus a very marked " intensification " had 

 taken place, and the problem of finding the cause was set 

 to the author. The seed-weight in F 2 gave an unexpected 

 frequency polygon ; instead of a 3:1 form we obtained a 

 modal curve, otherwise fairly symmetrical, which ranged 

 from 0'055 to 0170; the principal modes were situated 

 at 0-085, 0105, 0120, and 0140. 



Before discussing this graph any further we may note 

 that the F 3 data were of the same nature as those described 

 under the preceding character; the parental small seed 

 was extracted and bred true, while larger seeds sometimes 

 threw small ones in a way which suggested a 3 : 1 ratio, or 

 less commonly bred true. In the latter case a new 

 character, not found in either parent, had, been " fixed." 

 In the ordinary Mendelian characters such phenomena are 

 usually due to the meeting of cryptomeres, but we shall 

 see that our cryptomeres in this case are even less cryptic 

 than Miss Wheldale's enzymes in Antirrhinum. 



The attempt to dissect the F 2 grapli into its components 

 led to the plotting of numerous correlation tables, and to 

 the preparation of " dissected graphs " (Fig. 69). In the 

 latter method, which is more rapid than the former, we 

 take plants possessing some character in common, such as 

 a very large boll, and mark off their position on the graph 

 of the whole family. The mean of the special group, as 

 compared with the general mean, serves to indicate any 

 displacement, while the form of the " dissection " is usually 

 less complicated than that of the general graph. On 

 dissecting in this way for the fifteen plants which had the 

 greatest boll-width of the whole 181 F 2 individuals, the 

 mean seed- weight was raised by 0105 g. ; moreover, 

 though these large-boll plants constituted the greater part 

 of the 0140 mode, yet four of them were found in the - 085 



