THE OUTLOOK FOR PLANT BREEDING. 95 



methods has been introduced, and for many years now hundreds of 

 thousands of beets have been examined every year in order to find 

 the ones highest in sugar content to use as mothers in seed production. 

 The industry has grown and come to be dependent on this continu- 

 ous selection, yet even after these many years of selection, the highest 

 sugar content ever found is only about 26 per cent and this is of very 

 rare occurrence, so rare, indeed, that one can readily believe that 

 had Louis Vilmorin, in his time, been able to have made a hundred 

 thousand analyses, he would have found a similar high per cent 

 occasionally. The whole experience of the industry shows that the 

 selection must be kept up every year if we are to maintain a high 

 mean per cent and that as soon as the selection is discontinued, the 

 reversion to a lower mean is very rapid. It would seem therefore, 

 that we are forced to conclude that this continuous selection has 

 added no new permanent character to the race. It would seem that 

 here, with all the care and years of selection, there has been no cumu- 

 lative effect. It may be objected that in this case we are dealing 

 with a physical impossibility as it is clearly impossible to have a beet 

 all sugar, and we may be too near the limit of physical possibilities. 

 In answer, the mutationist would say, that as 20 to 26 per cent of 

 sugar is not infrequent, the selection should have produced a race 

 having a mean that would remain permanently higher, and in this 

 claim they would appear to be justified. 



The experiments carried on at the Illinois ExjDeriment Station in 

 the selection of corn to increase and decrease the oil and protein 

 contents are very interesting in this connection. Starting with an 

 average protein content of 10.92 per cent and selecting each year for 

 propagation those individuals having the highest protein content, 

 the mean per cents through twelve years of selection run as follows : 

 11.10, 11.05, 11.46, 12.32, 14.12, 12.34, 13.04, 15.03, 14.72, 14.26, 

 13.89, 13.89. 



It will be seen that the average protein content has continued 

 gradually to increase. On the other hand, starting with the same 

 strain having an average protein content of 10.92 per cent and 

 selecting each year for propagation those individuals having the 

 lowest protein content, the mean per cents through twelve years 

 of selection run as follows: 10.55, 10.55, 9.86, 9.34, 10.04, 8.22, 

 8.62, 9.27, 8.57, 8.64,, 7.32, 8.95. 



