346 
AMERICAN JOURNAL OF BOTANY 
[Vol. 8, 
section of table i. The straight-line equations showing the regression of 
the number of bundles in the central region of the hypocotyl are recorded 
and represented graphically on diagram 3 for trimerous seedlings and on 
diagram 4 for dimerous seedlings. These diagrams, like the two preceding, 
also give the regression equations and their graphic representation for the 
epicotyl which will be discussed in a subsequent section. 
The correlation coefficients are positive in all cases, and with one ex- 
ception may be considered statistically significant. They show, however, 
a considerable irregularity from line to line, presumably because of the 
varying range and distribution of number of intercalary bundles. The 
average value of the coefficient is +.2376 for trimerous seedlings and 
+ .6290 for dimerous seedlings. 
Turning to the graphs, we may note that for the dimerous plants the 
agreements between the empirical and the theoretical means are very good 
indeed. The slope of the lines for the hypocotyl is very steep. 
The graphs for the trimerous plants show far greater irregularities be- 
cause of the generally small number of the strands but the occasional oc- 
currence of plants with a larger number. Reference to the tables will 
show that in line 75 there is one seedling with 6 intercalary bundles whereas 
the remaining 141 seedlings have only o, i, or 2 intercalary bundles. In 
line 93 there is only one seedling with more than 2 intercalary bundles and 
it has 4. In line 98 all the frequencies with two exceptions fall on o or I 
intercalary bundle. 
The correlations and equations have been recalculated, leaving these 
extreme cases out of account. The regression straight lines based on all 
the material are represented by solid lines. Those in which the extreme 
class were omitted are represented by broken lines.^ The removal of these 
aberrant cases has increased the agreement between the observed and the 
theoretical means but the fit is still far from satisfactory. The only con- 
clusion which can be drawn from these diagrams is that there is a con- 
siderable degree of positive correlation between the number of the inter- 
calary bundles and the number of bundles in the hypocotyl. 
Total Basal Bundles and Mid-region of Hypocotyl 
The correlations between total bundles (primary double bundles + in- 
tercalary bundles) at the base of the hypocotyl and the number of bundles 
in the central region of the hypocotyl, Yhh, are shown in the third section of 
table I. The straight-line regression equations are given and represented 
graphically as the lower figures in each panel of diagram 5 for trimerous 
seedlings and diagram 6 for dimerous seedlings. 
As might be expected on a priori grounds, these coefficients agree with 
those for primary double bundles and for intercalary bundles in sign, and 
2 For the curtailed series the regression equations are: Line 75, H = 12.194 -\- 0.654/; 
Line 93, H = 12.238 -\- 0.462 /; Line 98, H = 12.030 -f 0.473 /. 
