Feb., I92i] HARRIS AND OTHERS — SEEDLINGS OF PHASEOLUS 
lOI 
In both types of seedlings, but more frequently in the normal ones, 
additional or intercalary bundles appear in the hypocotyl, either de novo 
or as a result of division of the primary strands. 
The following constants^^ (table 19) for bundle number (at the different 
levels studied) epitomize the differences which characterize the two types 
of seedlings. 
Table 19 
Trimerous Seedlings 
Dimerous Seedlings 
Mean 
S. D 
C. V. 
Mean 
S. D. 
r V 
Root nolp^ 
5.02 
•654 
13.02 
4.01 
.081 
2.03 
Maximum 
5.16 
•739 
14.47 
4.13 
.338 
8.18 
Mean 
5-09 
•707 
13-87 
4.05 
.171 
4.19 
Primary double bundles 
Minimum 
5-81 
.288 
4.86 
4.02 
.140 
348 
Maximum 
5.98 
.581 
10.01 
4.52 
.666 
14.74 
Mean 
5.91 
405 
6.87 
4.19 
.411 
9.66 
Intercalary bundles 
Minimum 
.09 
.292 
156.62 
.07 
.261 
105.79 
Maximum 
.29 
.686 
381.67 
•83 
1.024 
355.48 
.19 
.491 
274.92 
49 
.687 
182.70 
Mid-region of hypocotyl 
Minimum 
11.99 
•532 
4.42 
8. II 
.409 
5.04 
12.29 
1.283 
10.44 
10.62 
1.645 
17.34 
Mean 
12.16 
.883 
7.24 
9-23 
1. 193 
12.67 
Mid-region of epicotyl 
Minimum 
14.89 
1. 152 
7-74 
12. II 
.406 
3.35 
16.10 
1750 
10.87 
12.36 
.757 
6.13 
Mean 
1547 
1.383 
8.92 
12.22 
.586 
4.79 
The variability of root pole number is distinctly higher in trimerous than 
in dimerous seedlings, because of the fact that in all seedlings a four-poled 
condition is characteristic of the main root system and prevails even in 
the trimerous forms up to within a few millimeters of the base of the hypo- 
cotyl. Sections in the upper root region in such seedlings therefore show a 
considerable number of four- and five-bundled individuals. 
The number of intercalary bundles is highly variable in both seedling 
types. The standard deviation is distinctly larger in the dimerous forms, 
but because of the generally lower average number of intercalary bundles in 
trimerous seedlings, the relative variabilities as measured by the coefficient 
of variation are higher in the trimerous type. 
In the central region of the hypocotyl the variability of bundle number, 
both absolute and relative, is far higher in the dimerous seedlings, due in 
large part to the generally higher standard deviation of the number of 
intercalary bundles in the dimerous type. 
In the central region of the epicotyl just the reverse is true, the varia- 
bility of bundle number being higher in the trimerous than in the dimerous 
seedling. This is evidently due to the facts (a) that the intercalary bundles 
^2 Data for number of root poles are available for only three of the five lines. 
