Oct. IS. 1914 First-Generation Maize Hybrids 87 



parents and the hybrids the average yield represents the mean yielding 

 power of the four parent plants, the only difference being the way in which 

 the individuals are combined. 



To secure the most accurate comparison of the yield of the four ears, 

 one seed from each of the ears was planted in each hill. The different 

 kinds were identified by their relative position in the hill. To place the 

 seeds accurately, a board 4 inches square was provided with a small, 

 pointed peg 2 inches long at each corner. These pegs were forced into 

 the soil at each hill, making four holes, one for each of the four kinds, 

 only one seed being planted in a hole. The board was always placed with 

 two sides of the board parallel to the row. It was necessary to exercise 

 extreme care in dropping the seeds to avoid changing the position of the 

 kinds. The best way to obviate mistakes of this kind is to make all the 

 holes of a row in advance and to go down the row with one kind of seed 

 at a time. 



At harvest time the seed produced by each plant was weighed and 

 recorded separately. All hills that lacked one or more plants were 

 excluded and the comparison confined to hills in which all four kinds were 

 represented. The method of handling the yields was to determine the 

 mean yield of the four kinds in each hill and to state the yield of each of the 

 four plants as a percentage of the mean of the hill in which it grew. The 

 percentage standing of each kind in all the hills was then averaged to 

 secure the final expression of the relative behavior of the four kinds. 



This method of comparison is similar to the ingenious plan originated 

 by C. H. Kyle,' for use in ear-to-row breeding. Kyle's method is to plant 

 each of the ears to be tested in a separate row and in each hill to plant 

 one seed of a standard, or check, ear with which all ears are compared. 

 Since comparative and not absolute yields are desired in the study of 

 hybrids and with only four kinds to compare, the introduction of a check 

 in the present experiment would have increased the space occupied by 

 the experiment without lessening the experimental error. 



APPLICATIONS OF METHOD 



The hybrid tested by this method was a cross between the Egyptian, a 

 white sweet com, and the Voorhees Red, a related sweet variety with red 

 aleurone.^ The two hybrids secured in accordance with the foregoing 

 method were designated PhgS and Phgj. The use of the Voorhees Red 

 variety as one of the parents made the comparison unusually difficult. 

 This variety produces a considerable percentage of albino seedlings, and 

 since no albino seedlings reach maturity, the result was a large number of 

 hills with less than the full complement of plants. Eighty-four hills were 

 planted, but only fifty-eight matured plants of all four kinds. 



The comparative yield of the four kinds is given in Table I. To illus- 

 trate the meaning of these determinations, let us take the yield of the 

 Egyptian variety. The number 112,8 indicates that the yield of 58 

 Egyptian plants averaged 112.8 per cent of the mean yield per plant of 

 all four kinds— that is, 12.8 per cent above the mean. 



* Kyle, C. H. Directions to cooperative com breeders. U. S. Dept. Agr., Bur. Plant Indus., B. P. I. — 

 564, 10 p.. 1910. 



*The strain of EgMitian com used in this experiment was from commercial seed secured from J. M. 

 Thorhuni & Co. iu 191 1. Tlie original source of the Voorhees Red was an ear kindly supplied by Prof. 

 Byron D. Halsted, of the New Jersey State Agricultural Experiment Station, in 1907. 



