130 



EDGAR ANDERSON AND WILLIAM L. BROWN 



and Northern Flints. Our experiments in crossing a typical white gourdseed 

 from Texas and a typical yellow flint from New York State are now only in 

 the third generation and are being continued. However, it is already evident 

 that some of the segregates from this cross are within the range of varia- 

 tion of Corn Belt dents (Fig. 8.3). 



In spite of the 50 to 100 generations of mixing which has taken place, the 

 characters of Northern Flints and Southern Dents still tend to be associated 

 in Corn Belt dents. Anderson (1939) has shown that in crosses between species 



10 



OLD SOUTHERN OENTS 



10 



> 

 u 



Z 

 lit 



3 



a 



^20 

 li. 



10 



DERIVED SOUTHERN OENTS 



CORN BELT INBREDS 



10 



NUMBER OF CHROMOSOME KNOBS 



Fig. 8.2 — Frequency distribution of chromosome knobs in Northern Flints, Southern 



Dents, and Corn Belt inbreds. 



or between races, all the multiple factor characters which characterize each 

 are partially linked with one another and tend to remain associated, even 

 after generations of controlled breeding. More recently he has used this 

 principle in the development of the method of extrapolated correlates (Ander- 

 son, 1949) by which the original characteristics can be deduced from the mix- 

 tures even when previously unknown. 



Using this method in a relatively crude form, we were able (in advance 

 of our historical evidence) to demonstrate (Brown, 1949) in Corn Belt in- 

 breds, the association of low knob numbers, flag leaves, cylindrical ears, few 

 tassel branches, and flinty kernels — all characteristics which typify the 

 Northern Flints. Similarly, it was possible to show the association among 

 these 98 Corn Belt inbreds of high knob numbers, no flag leaves, tapering 

 ears, dented kernels, and many tassel branches — a combination of char- 



