No. 528] INHERITANCE IN PLANTS 



746 



variation is deferred until F 2 . While predictions can 

 not be made with much assurance before F 3 has been 

 studied, it seems probable, nevertheless, as suggested 

 by East, 11 that we shall eventually find that sizes and 

 shapes are not simple characters, but that a particular 

 mean size in reality depends upon two or more, perhaps 

 upon several, distinct factors, a part, or all, of which 

 exhibit incomplete dominance. If this were true, we 

 should expect intermediates (blends) in F 2 and a range 

 of variation from one parent to the other, or sometimes 

 even beyond the parents, in F 2 just as we do find in case 

 of many plant characters. It should also follow that 

 certain F 2 sizes breed true in F 3 while others continue 

 to break up, the variation in some eases extending over 

 the same range as in F 2 and in other cases over variously 

 restricted ranges. There is some evidence that this sug- 

 gested behavior in F 3 occurs not only in regard to size 

 characters, but also in case of certain colors where 

 blends are seen in F,, but observations are as yet too 

 meager to be presented. 



I am of course not unmindful of the many chances for 

 mistakes in interpretation of the facts secured in a study 

 of size and shape characters. In the apparently simple 

 cases of height of maize stalks or of bean plants, it must 

 be remembered that parents differing in height may also 

 differ in number of nodes, so that segregation in the 

 latter character might bring about differences in height. 

 Number of nodes and average internode length must both 

 be studied instead of merely the product of these, actual 

 height. Or perhaps, parents can be found that differ in 

 height but have the same number of nodes. Confusion 

 resulting from increased fluctuations due to differences 

 in soil and season can be lessened by growing some 

 plants of all generations to be studied in the same sea- 

 son (from seed kept for the purpose or by repeated 

 crosses), and on as uniform soil as can be had. Even in 

 the same summer plants with different periods of de- 



"East, E. M., Amer. Nat., 44: 



72, 73 (1910). 



