74 
AMERICAN JOURNAL OF BOTANY 
[Vol. 8 
associated with an increase of fifty percent in the number of cotyledans and 
leaves. The distributions show, however, that this is only an incomplete, 
and to some extent an erroneous, statement of the condition. In the 
dimerous seedlings the modal number of primary double bundles is 4, and all 
departures from the modal number are higher. In the trimerous seedlings 
the modal number is 6, and the departures may be in either the positive or 
the negative direction. The frequency distribution for the dimerous plants 
is therefore wholly skew, forming a typical J-curve; that for the trimerous 
plants more or less symmetrical,^ but with departures occurring chiefly as 
smaller numbers of bundles. 
The variation of primary double bundle number in dimerous and trim- 
erous plants is, therefore, transgressive. The number of externally dimerous 
seedlings which might be considered to be anatomically trimerous, and the 
number of trimerous seedlings which might on anatomical grounds be 
considered dimerous is, however, very small. 
Turning to the physical constants in table 4, we note that the mean 
Table 4. Statistical constants for number of primary double bundles at base of hypocotyl of 
trimerous plants and their normal controls 
Mean 
Standard Devi- 
ation 
Coefficient of Vari- 
ation 
Line 75 
Actual difference 
Relative difference 
Line 93 
Trimerous (N = 155) 
Dimerous (N = 155) 
Actual difference 
Relative difference 
Line 98 
Trimerous (N = 183) 
Dimerous (N = 183) 
Actual difference 
Relative difference 
Line 139 
Trimerous (N = 106) 
Dimerous (N = 150) 
Actual difference 
Relative difference 
Line 143 
Trimerous (N =221) 
Dimerous (N = 221) 
5.98=b.02 
4.22 ±.03 
0.436^.017 
0.505 ±.020 
7.28 ±.29 
1 1.97 ±.49 
H-i.76±.04 
41.71 
5.90±.02 
4.52=t.04 
— 0.069 d=. 026 
13-66 
o.396±.oi5 
o.666±.026 
-4.69i.56 
6.72±.26 
14.74i.58 
+ i.38=b.04 
30.53 
5-93±.oi 
4. 12 ±.02 
— 0.270zb.030 
40.54 
0.288 =b. 010 
o.427=b.oi5 
-8.02 ±.63 
4.86±.i7 
10.36zb.37 
+ I.8l=b.02 
43-93 
5.91 ±.02 
4.02=b.OI 
— o.i39±.oi8 
32.55 
o.323±.oi5 
o.i40±.oo5 
-5.50dz.41 
5-47±-25 
3.48 zb. 14 
+ i.89±.02 
47.01 
5.81 ±.03 
4.07 d=. 01 
+o.i83±.oi6 
130.71 
0.581 d=.oi9 
o.3i5it.oio 
+ i.99±.28 
10.01 zt.32 
7-75±-25 
Actual difference 
Relative difference 
+ i.74±.03 
42.75 
' +0.266rt.02I 
84.44 
+ 2.26=t.4I 
^ Line 139 is probably only an apparent exception to this rule. In both dimerous and 
trimerous seedlings variations from the modal class are extremely rare, and variations 
above the modal class have not been found in the 106 trimerous seedlings of this line 
sectioned. 
