INHERITANCE IN THE BARLEY SPIKE. 17 



FAMILY HANNA (460) X EEID TRIUMPH (404). 



The parental forms, Hanna and Reid Triumph, are of distinctly 

 different densities, and there is no overlapping of frequency distri- 

 butions during the three years in which they have been grown. In 

 Table II (sec. D) the mean of the Hanna parent ranges from 

 4.12 ±0.02 mm. in 1916 to 4.56 ±0.01 mm. in 1918. The Reid 

 Triumph variety has much less seasonal variation, the mean in 1917 

 being 2.73 ±0.01 mm. and in 1916, 2.64 ±0.01 mm. It is of interest 

 to note that the Reid Triumph has about the same average mean as 

 the Svanhals 2-rowed form, while the Hanna is considerably more 

 lax than the Manchuria form which was crossed with the Svanhals 

 variety. 



The F 2 generation of the cross between Hanna and Reid Triumph 

 proved more variable than the parents and frequently gave distri- 

 bution from below the mode of the Reid Triumph to considerably 

 above the mode of the Hanna parent. Twenty F 2 plants were grown 

 in F 3 , some giving as variable a population as obtained in F 2 , while 

 other F 3 lines were no more variable than the parental forms. 



Fourteen of these F 3 lines which gave the clearest indication of 

 being homozygous were further tested in the F 4 generation. The 

 method was similar to that previously used, 4 to 10 plants of a line 

 being grown and the combined result being the basis of conclusions 

 as to purity. Of the 14 lines tested in F 4 , 8 gave evidence ill the com- 

 bined F 3 and F 4 data to show that they are homozygous for density. 



Those which are of questionable purity will be briefly considered. 

 Selection 406-3 gave a mean of about the same density as the Reid 

 Triumph parent, but the coefficient of variability is somewhat higher 

 than in the pure parental lines. Selection 406-4 proved to be 

 heterozygous. One of the head selections, 406-4-3, produced a type 

 which seems pure for density. The mean of this line is 3.72 ±0.03 

 mm. Selection 406-9 seems to be heterozygous. Probably 406-9-1 

 is homozygous, the average mean being about the same as that of 

 the Hanna parent. Selection 406-10 also is more variable than the 

 pure parental variety. The frequency distribution indicates that 

 fewer density factors are involved than in the F 2 generation. Selec- 

 tions 406-16 and 406-18 appear to be heterozygous. In later gen- 

 erations two selections of 406-18 seem to be homozygous. Thus 

 406-18-5 is probably breeding true with a mean density of 3.40 ±0.02 

 mm,., while 406-18-9 gives evidence of being homozygous for a 

 mean of 2.66 ±0.02 mm. 



Those which seem nearly homozygous by an examination of their 

 frequency ranges and coefficients of variability as obtained in F 3 

 and F 4 generations are as follows: 406-1, mean 2.81 ±0.01 mm.; 

 406-5, mean 4.43 ±0.01 mm.; 406-7, mean 2.43 ±0.01 mm.; 406-8, 

 mean 4.32±0.01 mm.; 406-11, mean 4.32±0.02 mm.; 406-12, mean, 



