■i 30 MAIZE 



CHAP, saved was therefore limited. It was also found that in Some 

 v ' cases in the same breed there was a difference of nearly two 

 weeks in the time of flowering. This experiment demon- 

 strated clearly that close planting, even allowing two weeks 

 between plantings, cannot be relied upon to prevent cross- 

 pollination. 



By planting first an early-maturing breed, and two weeks 

 later a late-maturing breed, a certain degree of immunity may 

 be secured. But there would be little practical advantage in this, 

 except where it is necessary to plant several breeds in close 

 proximity, for the farmer usually desires to plant all his late- 

 maturing maize first, and afterwards that which takes less time. 



The use of rows of sorghum and kaffir-corn to separate the 

 different sorts has proved unsatisfactory on the Transvaal 

 High-veld, the maize having come into flower before the sor- 

 ghum was tall enough to afford any protection. 



Detasselling is perhaps the most satisfactory method of deel- 

 ing with the problem. But there is a certain amount of fluctuat- 

 ing variability as regards time of flowering, and variability will 

 be still more pronounced where the strain is heterozygous for 

 this character. In practice this means that detasselling must 

 be repeated (in the same row) two or perhaps three times within 

 a week or ten days, and that great vigilance must be exercised 

 to detect individual plants which flower later than others, and 

 prevent pollen scattering from their earliest anthers. 



Covering the plots with cheese-cloth was tried at the 

 Government Experiment harm, Potchefstroom, as a means of 

 isolating the breeding plots, but was not found satisfactory. 



185. Production of X cio Types by Artificial Cross-pollination. 

 — The popular idea of cross-breeding maize is that by crossing 

 two sorts the result will be a hybrid combining the characters 

 of the two parents. This may be the case with the first ear 

 obtained by the cross, but it is not always the case in the pro- 

 geny of the first generation. Experience shows, moreover, 

 that even where it does occur, the second generation from the 

 cross produces a great deal of variation, more particularly with 

 moncecious plants like maize, and unless scientifically guided 

 efforts are made, this variation will continue from generation 

 to generation tor an indefinite period. We have already dis- 

 cussed the reason for this mixture of characters, and how it 

 may be avoided or made use of. 



