1907-] PLANT BREEDING PRINCIPLES AND RESULTS. 125 



For the first quarter " tasseled seed " is brought from the 

 fourth quarter, for the fourth quarter from the second, for 

 the second from the third, and for the third from the first. 

 This is done in order to carry the seed to bear " tasseled stalks " 

 as far away as possible from their sister ears, which are to 

 remain in the quarter in which they grew and produce 

 " detasseled stalks." 



The remainder of the plan for planting is explained in Bui. 

 No. 152 of this Station. It is simply a mathematically worked 

 out plan in which ears of corn from the same mother ears are 

 year by year kept separated from each other as far as is pos- 

 sible on this size breeding plot : that is, the rows on either side 

 of a tasseled row, — by which row they are in a great measure 

 pollinated, — are planted the next year with more than one 

 row between them. 



These plans can be easily worked out by the breeders, but 

 should any difficulty be encountered, this Station will be glad 

 to give any necessary help. 



Dangers of Inbreeding. 



Our reasons for taking so much trouble to avoid inbreed- 

 ing, are definite deductions from exact experiments. In a 

 long series of careful investigations, the great Charles Darwin 

 found that plants usually cross-pollinated, suffer great 

 deterioration when self-pollinated or inbred. Other plants, 

 such as wheat and tobacco, have through long ages become 

 accustomed to inbreeding and suffer no ill effects from it. 

 Corn, however, is a wind pollinated plant, and is to a great 

 extent cross-pollinated. It has been found, though, by many 

 observations on the time of maturity of the male and female 

 flowers of the corn plant (the tassels and the silks) that when 

 left to natural pollination by the wind, a considerable amount 

 of self-pollination ensues. This does not have an ill effect 

 upon the general field of corn, for here we save a few ears 

 from a very large number of probably unrelated ears for the 

 next year's planting, and sell or feed the remainder. In the 

 breeding plot we have entirely different conditions. There, 

 we are breeding from year to year, kernels from only a small 

 number of ears which must necessarily be of closely related 

 blood lines : and we must assure ourselves that there self-polli- 

 nation does not take place, by detasseling the rows from which 



