190 Segregation of a Quantitative Character in Beans 



To test further the constancy of the M segregated types the longest 

 four and the shortest (7) plant from row 22 were used as seed again in 

 1918 giving rows 46, 47, 48, 55 and 56. It will be seen that these give 

 identical curves corresponding in type to the control curves for M in 

 1918. Further the two groups 18 and [20, 22], sown in duplicate from 

 the seed of one plant in 1914, were continued in 1916, and row 20 from 

 group 18 in 1918. It will appear also from their curves that their seed 

 corresponds with the control M types and with the Ms segregated from 

 group 21. 



Group 12 behaves in a similar manner. In 1915 three M types, two 

 extremely short, three apparent Es and one doubtful were selected for 

 seed. In 1916 the Ms bred true, the Xs bred true and the apparent Es 

 and the doubtful type split. Of particular interest in this group are the 

 curves for rows 23, 24, 25, 26, 27 and 28 in 1918, representing selected 

 short (23, 24, 25) and long (26, 27, 28) variates from an X group in 

 1916. The curves are identical, indicating again that the X type is 

 homozygous and that therefore selection has no effect in altering the 

 type. 



Row 10 (1916) appeared of a rather doubtful composition. Although 

 in general M in type, there were two doubtful, possibly intermediate 

 plants, and one which produced certainly very few beans, but these so 

 short that the possibility at least of something unusual had to be 

 admitted. These were therefore sown ; rows 9 (ext. short) and 13 and 

 14 (intermediate), with two of the longest types from row 10, rows 10 

 and 11. The curves show no difference of significance; the difference 

 between 13 and 14, which seems the greatest, is in any case not greater 

 than that between 68 and 18 of the control pure Ms. 



In groups 5 and 14 occurred the only serious disturbance that arose, 

 in that types selected as X did not in every case j)rove to be X. In 

 view of the subsequent behaviour of their descendants they must, 

 however, be regarded as very aberrant members of the intermediate 

 heterozygous group usually selected as apparent Es. There is always 

 transgressive variation, and 1916 was a very bad year. It will appear 

 that other types too suffered, the beans being shorter than usual ; and 

 as the chief cause was, no doubt, that the ground was " bean-tired," the 

 shifting of the types to the left had probably begun in 1915. 



In group 5, then, there were selected in 1915 four supposed X plants, 

 four E and two intermediates. In 1916 only one of the rows from sup- 

 posed A'' seed bred true. The other three and the four Es showed 

 segregation, while the two intermediate proved to be M. It is signi- 



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