Feb., I92i] HARRIS AND OTHERS — SEEDLINGS OF PHASEOLUS 
71 
We shall consider in order the levels at which sections were made, begin- 
ning at the root. 
I. Root. Roots were sectioned in the cases of lines 93, 139, and 143. 
The numbers of bundles^ in the roots of normal and trimerous seedlings of 
these lines are shown in table i . 
Table i 
Primary 
Double 
Bundles 
Line 93 
Line 
139 
Line 143 
Trimerous 
Dimerous 
Trimerous 
Dimerous 
Trimerous 
Dimerous 
3 
4 
31 
132 
2 
15 
149 
4 
37 
219 
5 
87 
20 
53 
I 
113 
6 
34 
36 
66 
7 
I 
The entries in this table show that most of the normal plants are tetrarch, 
although a small percentage are pentarch. In the trimerous seedlings the 
highest percentage are pentarch, but the remainder are distributed between 
tetrarch and hexarch with a few in more extreme classes. Sections made at 
progressively lower levels in the root show that the hexarch and pentarch 
conditions, in the trimerous seedlings, soon give way to tetrarch. This 
fact doubtless explains the relatively large number of non-hexarch cases 
Table 2. Vascular formula for base of hypocotyl of trimerous seedlings and their normal 
controls 
Base of 
Hypocotyl 
Line 75 
Line 93 
Lin 
e 98 
Line 
139 
Line 143 
Trimer- 
ous 
Dimer- 
ous 
Trimer- 
ous 
Dimer- 
ous 
Trimer- 
ous 
Dimer- 
ous 
Trimer- 
ous 
Dimer- 
ous 
Trimer- 
ous 
Dimer- 
ous 
(4) 
(4) + I 
(4) +2 
(4) +3 
(4) +4 
(4) +5 
(4) +6 
(5) 
(5) + I 
(5) +2 
(5) +3 
(6) 
(6) + I 
(6) + 2 
(7) 
(7) + I 
(7) +2 
(8) 
(8) + I 
I 
I 
8 
2 
107 
12 
2 
7 
I 
I 
69 
30 
10 
4 
2 
2 
13 
4 
I 
I 
5 
I 
I 
5 
10 
3 
120 
II 
I 
4 
34 
37 
I 
22 
18 
9 
10 
3 
2 
I 
4 
6 
I 
160 
10 
I 
97 
43 
23 
2 
6 
8 
I 
I 
I 
I 
I 
4 
4 
138 
9 
I 
2 
2 
3 
15 
31 
134 
25 
5 
4 
150 
55 
4 
5 
5 
I 
I 
142 
142 
155 
155 
183 
183 
106 
150 
221 
221 
^ Where the bundles were united in a ring, the number refers to number of protoxylem 
strands. 
