No. 545] SHORTER ARTICLES AND DISCUSSION 



303 



The corn index number has the following formula 



A + 3^ + 2(7 

 1_ D + E + F 2 ' 



The definition of the variable C given on p. 393, by an un- 

 fortunate slip of the pen, which escaped detection in the proof, 

 as such things will, gives precisely the inverse effect from what 

 it should. The equation should read as follows : 



C— 100 — t * meS the circumference of tne C0D at middle 

 Circumference of ear at middle 



The example on p. 399, which was worked out after the text 

 was written, followed the erroneous text with scrupulous exacti- 

 tude in theory, but with a slip in the arithmetic. The correct 

 value of I x for the ear used as an example is 



190.0 + 70 .5 4- 77.6 _ 338.1 

 1 " 21.6 + 2.8 + ~ ~UA ~ 



Experience in the use of this index suggests that in the equa- 

 tion for C given above it may be advantageous to substitute 

 " diameter" for "circumference" in each case. The diameters 

 can be much more easily and accurately measured and they 

 probably give a better appreciation of the relative kernel depth 

 than do the circumferences. 



II. A Selection Index Number for Beans 

 The writer has under way at the present time some breeding 

 experiments with a very interesting variety of beans, known 

 locally as the "Old-fashioned Yellow Eye." It is a variety ap- 

 parently scarcely known now outside of northern New England. 

 Owing to certain defects it has been replaced in most of the bean- 

 growing sections of the country where formerly grown by the 

 Improved Yellow Eye, a perfectly distinct and in many respects 

 inferior type. From the standpoint of experimental genetics 

 the old-fashioned yellow eye bean promises to furnish material 

 of great interest and value in the unraveling of such problems 

 as pattern inheritance, the effect of selection in pure lines, etc. 

 Aside from the technically biological considerations, however, 



