A Genetic Study of Plant Height in Phaseolus Vulgaris. 41 
to that of Snowflake. The fact, however, that the mean-length 
ratio for Snowflake and Triumph is considerably greater for five 
internodes than for four, suggests that it might be still greater 
if it were possible to determine it for a greater number of inter- 
nodes. The only conclusion that can be drawn from the com- 
parison is the rather indefinite one that the potential internode 
length of Triumph is less than that of Snowflake, but probably 
not so much less as is indicated by the mean-length ratio for the 
first five internodes, 100:64. By similar reasoning it is concluded 
that Red Marrow has a potential internode length greater than 
that of Snowflake, the difference probably being more than is 
indicated by the mean-length ratio for the first five internodes, 
100:92. Likewise, it may be said that the potential internode 
length of Triumph is considerably less and that of Red Marrow 
somewhat less than that of July. The direct comparison between 
Red Marrow and Triumph would appear reliable, for the reason 
that mean-length ratios are not far different when the comparison 
is made at the end of any internode from the first to the fifth. 
There is, however, a gradual increase in the ratio after the first 
internode. It would seem safe, therefore, to conclude that the 
potential internode length of Triumph is considerably less than 
that of Red Marrow but that the difference is probably not quite 
so great as is indicated by the mean-length ratio for the first 
five internodes, 100:58. 
The only method available for accurately testing the potential 
internode length of bush beans is to cross them with pole beans 
and compare the internode length of the indeterminately growing 
plants thus produced with that of the pole-bean parent. For 
such a comparison the F2 generation of the cross is to be preferred 
to the Fi generation, because increased vigor due to heterozygosis 
is less in F2 than in Fi. There is an additional reason for this 
preference in case of beans. The difficulty in cross-pollinating 
bean flowers and the fact that only a few seeds are obtained 
from any one pollination, make it next to impossible to grow even 
moderately large numbers of Fi plants. Comparisons of the F2 
generation of Triumph-Snowflake (56 plants). Red Marrow- 
Snowflake (74 plants), and July-Snowflake (78 plants), with each 
other and with Snowflake, are given here: 
Internode No 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 
Snowflake 26 22 21 22 22 23 25 28 31 34 37 41 44 47 48 
Triumph-Snowflake 21 18 19 20 21 23 25 28 31 33 35 37 38 39 39 
Ratio 100: 81 82 90 91 95 100 100 100 100 97 95 90 86 83 81 
Internode No 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 
Red Marrow-Snowflake. . 25 22 23 26 28 30 34 38 42 45 48 51 54 55 56 
Snowflake 26 22 21 22 22 23 25 28 31 34 37 41 44 47 48 
Ratio 100: 104 100 91 85 79 77 74 74 74 76 77 80 81 85 86 
