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SCIENTIFIC AGRICULTURE 



May, 1921. 



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tiple-factor hypothesis by adding; up the factors which 

 must distinguish the successive pairs, are different from 

 the results obtained on the same hypothesis in a direct 

 cross between earliest and latest. This question has been 

 more thoroughly discussed in another paper (4). 



Throughout the course of the experiments a close 

 watch has been kept for the correlation of characteris- 

 tics with earliness or lateness in order to find whetlier 

 it is possible to combine extreme earliness with all other 

 desirable qualities. 



The great majority of the early segregates in all 

 crosses are small and unproductive. It is not possible 

 owing to gradations in size and productiveness to give 

 the exact proportion. The great preponderance of un- 

 productive plants among the early segregates is of 

 course to be expected if only on physiological grounds. 



Nevertheless there appears to be no absolute linkage in 

 this respect because some large, vigorous, productive se- 

 gregates breeding true to these characteristics and at the 

 same time as early as the early parent have been 

 secured in crosses between very early small parents and 

 standard varieties. But a very large number of F, and 

 later generations have to be grown in order to obtain 

 them. 



No linkage has been found with any other character- 

 istics. If manj^ factors for earliness are distributed 

 tlirough all the chromosomes, one of these factors might 

 be linked with a particular characteristic located in the 

 same chromosome. But all the other factors for eauli- 

 ness obviously would not be linked with this one. And 

 the effect of the single factor would not be missed out 

 of so many. 



